Abstract
Disclosed is a precisely controlled microphone acoustic attenuator that lowers the sound pressure level to minimize microphone distortion. The acoustic attenuator also serves as a protective microphone enclosure that reduces exposure to debris as well as environmental humidity and harmful gases.
Claims
1. A passive acoustic attenuator comprising: an enclosed volume comprising at least one aperture; a diaphragm assembly; and, a microphone.
2. The acoustic attenuator of claim 1 wherein the enclosed volume entirely contains the microphone.
3. The acoustic attenuator of claim 1 wherein: the enclosed volume partially encloses the microphone through a second aperture; and, a microphone inlet is sealed to the enclosed volume's second aperture.
4. The acoustic attenuator of claim 1 wherein the attenuator is reduced in net size for the same attenuation by the use of two attenuator sections.
5. The enclosed volume of claim 1 wherein the microphone is physically protected by being inside the enclosed volume.
6. The diaphragm assembly of claim 1 wherein the diaphragm assembly is removable and replaceable.
7. The diaphragm assembly of claim 6 wherein the diaphragm assembly is attached to a first aperture of the enclosed volume.
8. The diaphragm assembly of claim 7 wherein the diaphragm assembly passively reduces sound level coming into the microphone.
9. The microphone of claim 1, where in the microphone is miniature to sub-miniature in size.
10. The acoustic attenuator of claim 1 further comprising a microphone adapter ring, where the microphone adapter ring is sized accordingly to use the attenuator with differently sized miniature to sub-miniature microphones.
11. A method of picking up at least one speech sound comprising the steps of: enclosing a microphone in an acoustic attenuator that has at least one volume of space for attenuating an acoustic speech sound; screening the plosive energy of the speech sound; attenuating the speech sound via the acoustic attenuator; picking up the acoustic speech sound via the microphone; and, converting the acoustic speech sound into an electric signal.
12. The method of claim 1 further comprising the step of controlling the attenuation of the acoustic sound via modifying the volume of space of the attenuator.
13. The method of claim 1 wherein the microphone is enclosed in the volume of space for attenuating the acoustic sound.
14. The method of claim 1 wherein the step of screening the plosive energy of the speech sound produces even pressure of the voice sound so that the voice sound may be picked up by the microphone with minimal distortion.
15. The method of claim 4 further comprising the step of exhausting the voice sound through a decibel containment voice exhaust two-way voice valve.
16. A precisely controlled microphone acoustic attenuator comprising: an enclosed volume; a diaphragm assembly; an attenuator collar; an attenuator shell; a microphone adapter ring; and, a circular collar.
17. The enclosed volume of claim 16, comprising at least one aperture.
18. The diaphragm assembly of claim 16, comprising: a diaphragm stepped shoulder; a diaphragm flange; and, a diaphragm film.
19. The acoustic attenuator of claim 16 wherein the attenuator shell physically encloses a miniature to sub-miniature-sized microphone to physically protect the microphone.
20. The microphone adapter ring of claim 16 wherein the adapter ring is sized accordingly to use the diaphragm assembly with differently sized miniature to sub-miniature microphones.
21. The diaphragm assembly of claim 16 wherein the diaphragm assembly is removable and replaceable.
22. A passive acoustical attenuator for a microphone, said acoustical attenuator combining attenuation to lower a sound level of a sound introduced into the microphone with physical protection for the microphone, said acoustical attenuator defined by an enclosed volume of space bounded by a sound inlet at the proximate end, containing a diaphragm structure and bounded at the distal end by a sound outlet sealed to a microphone, wherein the sound entering at the proximate inlet is reduced in level according to the divider effect of acoustical compliances of the diaphragm and the enclosed volume of space that is approximately constant over a wide acoustical range of speech.
23. An attenuator as in claim 22 where the microphone to which it is attached is miniature to sub-miniature in size.
24. An attenuator as in claim 23 wherein the diaphragm structure is removable and replaceable.
25. An attenuator as in claim 24 where the attenuator is reduced in net size for the same attenuation by the use of two attenuator sections.
Description
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0053] The manner in which these objectives and other desirable characteristics can be obtained is explained in the following description and attached figures in which:
[0054] FIG. 1A is cross-sectional view of an embodiment of an acoustic attenuator;
[0055] FIG. 1B is a cross-sectional view of an acoustic attenuator with a microphone fully enclosed;
[0056] FIG. 2A is a perspective view of a diaphragm of the acoustic attenuator of FIG. 1;
[0057] FIG. 2B is a side view of the diaphragm of FIG. 3a;
[0058] FIG. 3 is an exploded view of an alternate embodiment of an attenuator;
[0059] FIG. 4A is a perspective view of an alternate embodiment of an acoustic attenuator with a microphone and a cylindrical collar;
[0060] FIG. 4B is a front view of the attenuator of FIG. 4;
[0061] FIG. 4C is a cross section of the attenuator of FIG. 4;
[0062] FIG. 5a is a perspective view of an alternate embodiment of an acoustic attenuator with a microphone and a cylindrical collar;
[0063] FIG. 5b is a frontal cross-sectional view of the alternative embodiment of an acoustic attenuator with the microphone and the cylindrical collar of FIG. 5a;
[0064] FIG. 5c is a cross-sectional view of the side of the alternative embodiment of an acoustic attenuator with the microphone and the cylindrical collar of FIG. 5a;
[0065] FIG. 6 is a perspective view of an alternate embodiment of an acoustic attenuator;
[0066] FIG. 7a is a frontal cross-sectional view of the alternate embodiment of the acoustic attenuator of FIG. 6;
[0067] FIG. 7b is a cross-sectional view of the side of the alternate embodiment of the acoustic attenuator of FIG. 7a;
[0068] FIG. 8 is an electrical circuit diagram of the acoustic attenuator of FIG. 1 in a free-field application;
[0069] FIG. 9 is an electrical circuit diagram of the acoustic attenuator of FIG. 1 in a small volume application;
[0070] FIG. 10 is an electrical circuit diagram of the acoustic attenuator of FIG. 1 in a small volume application with potential compromises resulting from either low or high frequencies;
[0071] FIG. 11 is a graph showing measured attenuation of seven 30 dB acoustic attenuators and microphone assemblies made with microphones of two different dimensions;
[0072] FIG. 12 is a graph showing sound pressure level at various distances from microphones with and without an acoustic attenuator;
[0073] FIG. 13 is a cross sectional view of the attenuator inside a telephone handset;
[0074] FIG. 14 is a cross sectional view of a decibel containment voice exhaust two-way voice valve;
[0075] FIG. 15 is a diagram of the acoustic attenuator used with a voice algorithm to accurately translate compromised or impaired speech at a close distance to the microphone; and,
[0076] FIG. 16 is a flowchart with the voice algorithm to translate speech from raw voice input to digital output.
[0077] In the drawings, the following reference numerals correspond with the associated components of the acoustic attenuator: [0078] 1—acoustic attenuator; [0079] 2—attenuator sound inlet; [0080] 3—attenuator collar; [0081] 4—attenuator shell; [0082] 5—microphone adapter ring; [0083] 6—attenuator sound exit; [0084] 7—enclosed volume; [0085] 20—attenuator diaphragm assembly; [0086] 21—diaphragm pocket; [0087] 22—stepped shoulder; [0088] 23—slot; [0089] 24—flange; [0090] 25—diaphragm film; [0091] 30—microphone; [0092] 31—microphone sound inlet; [0093] 32—microphone wiring; [0094] 33—microphone diaphragm; [0095] 34—microphone coil; [0096] 35—microphone magnet; [0097] 40—circular collar.
[0098] It is to be noted, however, that the appended figures illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments that will be appreciated by those reasonably skilled in the relevant arts. Also, figures are not necessarily made to scale but are representative.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0099] Generally disclosed is a precisely controlled microphone acoustic attenuator with protective microphone enclosure. In use, the attenuator may be disposed in a telephone handset and be used for voice to text dictation. In the preferred use, the attenuator with protective microphone enclosure may be used to assist users with impaired speech to communicate more effectively. The details of a preferred embodiment of an attenuator are described in connection with the figures.
[0100] FIG. 1A is a cross-sectional view of one embodiment of the acoustic attenuator 1. The embodiment features an acoustic attenuator 1 connected to a microphone 30 to passively decrease the sound pressure level of incoming sounds to minimize distortion on the output. The acoustic attenuator 1 is defined by an attenuator sound inlet 2, attenuator collar 3, attenuator shell 4, microphone adapter ring 5, attenuator sound exit 6, acoustic volume 7, attenuator diaphragm assembly 20, and microphone 30. The preferred embodiment of the acoustic attenuator 1 and its components is composed of metal, although alternative embodiments can be made of plastic or other material that is low in cost to manufacture, easy to stamp and mold, and sufficiently insulated against both sound waves and environmental hazards that could potentially damage a microphone. The microphone 30 is defined by a microphone sound inlet 31, microphone wiring 32, microphone diaphragm 33, microphone coil 34, and microphone magnet 35. When the attenuator 1 is attached to the microphone 30, sound, such as a human voice, first enters through the attenuator sound inlet 2, or diaphragm slot 3, and the attenuator diaphragm assembly 20. The diaphragm 20 passively reduces the sound pressure level as the sound passes through the diaphragm 20 into the interior of the attenuator 1, or the acoustic volume 7. The diaphragm assembly 20 is set in diaphragm slot 23 of the attenuator collar 3; the attenuator collar 3 is the outward-facing component of the acoustic attenuator and makes up the front plate of the attenuator shell 4. The sound moves through the acoustic volume 7 to the attenuator sound exit 6, which is opposite the attenuator sound inlet 2, and through the microphone diaphragm 33 and microphone sound inlet 31 to have the microphone translate the sound from mechanical to electronic signal.
[0101] FIG. 1B is a cross-sectional view of another embodiment of the acoustic attenuator 1 where the microphone 30 is placed within the acoustic volume 7; FIG. 1B has similar components and functions to FIG. 1A, with the difference being the placement of the microphone.
[0102] FIGS. 1b and 2b are detailed versions of FIGS. 1a and 1b, respectively. The figures illustrate two preferable embodiments that form the attenuator, although there are several other additional alternate embodiments. In FIG. 2b, the diameter of the final attenuator with a microphone is approximately the same as the microphone's diameter. If the relative compliance (capacitance) is such that Cpro is approximately equal to Ct, then the transducer diaphragm and Cpro could be identical. The relative size of Cvol to Ct is the ratio of the length of the chamber to the length of the microphone. For example, if Cvol≈Ct≈Crv, then the chamber length would be about the length of the microphone. In that case the attenuation would be about 8 dB. An alternate structure is shown by FIG. 1a [is this the same FIG. 2a?]. Note that the microphone is not shown in FIG. 1a [2a?] but would be the same microphone structure as shown on FIG. 2b. The attenuator structure in FIG. 1a would have Cpro=10*Ct and Cvol=16*Ct. The compliance of a diaphragm is proportional to the square of the radius (and inversely proportional to the cube root of the thickness) so to achieve Cpro=10*Ct, Cpro would have a diameter about 3.16 times the diameter of the membrane used to make Ct. To achieve Cvol=16*Ct, the diameter of the circular chamber would need to be 4 times that of the microphone. Note that the in both examples the attenuation could be varied by adjusting the length of chamber forming Cvol. In FIG. 2b this could be achieved by sliding the microphone further in or further out of the sleeving. In FIG. 1a, the walls forming Cvol could be telescoped back and forth to achieve the same effect. Additionally, microphone manufacturers can make it easier to achieve Cpro≈Ct because they could make additional microphone diaphragms and repurpose them as Cpro. Also, greater attenuation is more easily achieved by increasing the diameter of the chamber forming Cvol, and because of this FIG. 1a could be preferable to FIG. 2b.
[0103] Still referring to FIG. 2b, adjusting the attenuation also adjusts the sensitivity of the microphone. The adjustments can achieve better uniformity from microphone to microphone because the sensitivity of the base microphones normally varies by +/−3 dB to +/−4 dB according to industry specifications. Using smaller or larger pressure relief vents and appropriate acoustic inductances and resistances for high resonances and roll offs can also provide additional frequency shaping for the microphone's response.
[0104] FIG. 1b is an alternate embodiment of an attenuator. If space is a premium, FIG. 1b teaches how to appreciably increase the attenuation without appreciably increasing the volume. FIG. 1b depicts two Acoustic Attenuators in series, where each section as the capacitance for its diaphragm and for its volume. This concatenated approach essentially doubles the volume of the attenuator, but doubles the attenuation as expressed in decibels (dB). For example, taking a 30 dB attenuator and then doubling its volume only increases its attenuation to 36 dB. To get 60 dB attenuation would require a volume about 33 times the original. However, using two attenuators in series raises the attenuation to 60 dB while only doubling the volume.
[0105] FIG. 2a is a perspective view of one embodiment of the attenuator diaphragm assembly 20; the diaphragm assembly is defined by a diaphragm pocket 21, stepped shoulder 22, slot 23, flange 24, and diaphragm film 25. Suitably, the diaphragm enables passage of sound into the acoustic pocket or volume 7. In a preferred embodiment, the diaphragm assembly is composed of metal or plastic, much like the acoustic attenuator, to best be suitably molded and shaped into the necessary dimensions, although could also be composed of other suitable materials that provide similar benefits. The diaphragm film 25 is ideally composed of polyethylene terephthalate, or mylar, which is a polyester, although could also be composed of other suitable materials capable of damping incoming sounds in a similar manner. When placed into the attenuator 1, the diaphragm is inserted into the attenuator collar 3 to cover the attenuator sound inlet 2. The diaphragm assembly 20 contacts the collar 3 with the stepped shoulder 22, which, in a preferred embodiment, is affixed to the collar 3 with a dissolvable cement, although in other embodiments could be attached through removable adhesive or other means that allow the diaphragm assembly to remain closely affixed to the attenuator and prevent debris or other unwanted environmental hazards inside the attenuator or microphone.
[0106] FIG. 2b is a side view of the diaphragm assembly 20. The diaphragm flange 24 faces the external environment and is opposite the acoustic attenuator 1; the stepped shoulder 22 sits between the flange 24 and collar 3. The diaphragm film 25 is attached to the flange 24 and acts as an acoustic diaphragm; the film 25 reduces the sound pressure level of incoming sounds by damping the physical vibrations created by the incoming sound, before the sound enters the acoustic volume 7 and the microphone 30. Should any portion of the diaphragm assembly 20 become compromised, the entire assembly can be removed from the attenuator by stripping the adhesive holding the assembly 20 to the attenuator 1, replacing the damaged par or the assembly as a whole, and then reaffixing the assembly to the attenuator.
[0107] FIG. 3 is a perspective view of an alternate embodiment of an acoustic attenuator 1 with a microphone 30 and a circular collar 40; the circular collar 40 is an alternate method of attaching the attenuator 1 to the microphone 30 and functions as an increased acoustic volume 7, which increases the sound's attenuation before reaching the microphone sound inlet 31. In a preferred embodiment, the collar 40 is made of metal or plastic, the same material as the attenuator 1, to properly function as the acoustic volume 7, prevent sound from escaping, and be easily shaped and molded to the desired specifications, although in alternative embodiments may be made of other materials that meet these requirements. The collar 40 also allows the attenuator's sound pressure levels to be either increased or decreased by moving the microphone closer or further away from the diaphragm assembly 20 to find the ideal attenuation level before the two are sealed in place within the collar 40. When sealing the attenuator and microphone, if using a caustic adhesive such as cement, it is important to allow noxious vapors to escape to prevent damage to the diaphragm film 25; a small hole can be drilled in the wall of the attenuator to allow harmful cement vapors to escape while cement is applied. Once the cement is dried and the attenuator and microphone are affixed to the collar 40, the small hole can be filled with cement to restore use to the attenuator.
[0108] FIGS. 4a and 4b depict alternate views of the acoustic attenuator 1 and microphone 30 with the circular collar 40. Specially, FIG. 4a is a perspective view of one embodiment of the attenuator 1 and microphone 30 fixed within the circular collar 40 and FIG. 4b is a cross-sectional view of the attenuator and microphone fixed within the circular collar 40.
[0109] FIG. 5 is a perspective view of an alternate embodiment of the acoustic attenuator 1 showing the attenuator separate from the microphone 30 and the diaphragm assembly 20 removed; the diaphragm assembly 20 is affixed to the attenuator collar 3, to cover the attenuator sound inlet 1 to filter incoming sounds. The attenuator shell 4 is attached to the microphone 30 while leaving space between the attenuator collar 3 and microphone sound inlet 31, to form the acoustic volume 7; the microphone sound inlet 31 is placed inside the acoustic volume 7 so that the microphone inlet 31 is adjacent to the attenuator sound exit 6.
[0110] FIG. 5C is a cross-sectional view of the acoustic attenuator 1; the attenuator collar 3 has a space in its center to serve as the attenuator sound inlet 2, which is then filled with the diaphragm assembly 20. The space in the center of the collar 3 is preferably circular, although in alternate embodiments may be square, rectangular, triangular, or shaped in other styles that do not negatively affect the sound quality and do not add distortion. The attenuator shell 4 is attached to the edges of the microphone to form the acoustic volume 7 and to protect the microphone from debris or other harmful environmental conditions such as gases or humidity.
[0111] FIG. 6 is a perspective view of the acoustic attenuator 1 featuring the microphone adapter ring 5; the adapter ring 5 can be different sizes to allow for differently sized microphones with smaller diameters to be used with a single size acoustic attenuator 1. The microphone adapter ring 5 is preferably circular to accommodate most microphones, although in alternate embodiments may be square, rectangular, triangular, or shaped in other styles that do not negative affect sound quality and allow for consistent adhesion with a microphone. The microphone adapter ring 5 is preferably composed of identical material to the attenuator 1 it is used with to create a homogenous attenuator that will respond consistently to wear over time and any harmful external factors or environments.
[0112] FIGS. 8, 9, and 10 depict basic electrical analogs for the acoustic attenuator 1 and microphone 30. FIG. 8 depicts the attenuator's use in a free field, while FIGS. 9 and 10 depict the use in an enclosed cavity with FIG. 10 additionally showing additional elements that may cause or abate performance modifications. The analogs are divided into four sections which represent, in order, the operation of the mouth, the acoustic load, the attenuator, and the microphone 30. For FIGS. 8 and 9, Cda and Cva are capacitors in series, where Cda represents a diaphragm 20 and Cva represents an acoustic volume 7. The sound pressure level, Pal, coming from the acoustic load is divided such that the sound pressure level, Pva, across Cva is reduced proportionately. The microphone 30 also possesses a microphone diaphragm 33, Cdmic, and a volume, Cvmic, in series with each other. This combination can be represented by another acoustical capacitance, Cmic, with the microphone diagram 33 in parallel with the microphone volume.
[0113] The effects of the microphone acoustical capacitances must be considered when computing the attenuation unless the microphone diaphragm's capacitance is much lower than the attenuator volume's capacitance. If this is not true or if the exact calculation is wanted, Cmic may be measured with an acoustic compliance test system, which a person of ordinary skill in the art of microphone design or acoustical test measurements can design and build. However, the acoustical capacitance of a diaphragm, like the diaphragm film 25, is difficult to pre-calculate because it depends on the diaphragm's material, geometry, and tensioning. A preferred diaphragm film 25 made of mylar is the same material used for subminiature diaphragms in electret microphones and as the insulator in electrical capacitors. Mylar is readily available in various thicknesses applicable to subminiature systems, and when metalized it forms a barrier to problematic vapors that could potentially harm the microphone or its components. The addition of the metallization layer and the additional processes of forming, clamping, or tensioning make the formula for computing the capacitance difficult to generate from a theoretical model. However, the acoustical capacitance of a diaphragm, Cadia, is generally proportional to the area and thickness of the diaphragm.
[0114] In practice, an appropriate diaphragm design procedure would be to first select the diaphragm thickness that gave the best protective properties and the diaphragm area that seemed applicable. Next, acoustic capacitance would be measured with acoustic capacitance test equipment. The capacitance value would then be used to vary the diaphragm's area to achieve the desired capacitance so that, when used with a known fixed volume, the desired attenuation would be reached. Alternately, the attenuator's acoustic volume could be varied to achieve the desired attenuation. Accordingly, the design process is very flexible.
[0115] Specifically, FIG. 8 shows the electrical analog of the transfer of sound from its generation at the human mouth, to its transition to acoustic load, through the attenuator 1, and into a microphone 30. Suitably, FIG. 8 depicts an attenuator that preferably features a 6 mm face that is oriented at the chamber's open end or attenuator's acoustic volume 7. (See, e.g., FIG. 1A or 1B.) As noted above, the preferred diaphragm assembly is in the attenuator collar 3 and could have a diameter approaching 6 mm. Since the microphone 30 may be chosen with a much smaller diameter than the chamber or acoustic volume 7, the most efficient use of the space could be to place the microphone 30 internal to the acoustic attenuator with possibly the microphone end with the terminals just protruding from the volume 7. (See, e.g., FIG. 1B.) A mathematical computation shows that the microphone volume is (2.5 mm/2)2*π*2.5 mm=12.27 mm.sup.3. The external dimension of the chamber is (6.0 mm/2)2*π*10.0 mm=282.7 mm.sup.3. The chamber volume to microphone volume ratio is a factor of 23:1, meaning the microphone does not appreciably reduce the chamber volume. However, the acoustic volume's 7 walls must be accounted for, and the wall thickness can be assumed to be 0.25 mm. The new ratio yields an external dimension of 225.7 mm.sup.3 with a ratio of 18.39:1. As noted, the diaphragm film's 25 equivalent acoustic capacitance was approximately half the volume of the microphone, 6 mm.sup.3, which yields an attenuation of about 31 dB. Additionally, the frequency can be better shaped to the microphone's response using smaller or larger pressure relief vents for the low frequencies and appropriate acoustic inductances and resistances for high resonances and roll offs. While the preferred embodiment is combining the attenuator 1 with a single sound inlet microphone, or a unidirectional microphone, in an alternate embodiment the acoustic attenuator 1 could be used with a multiple sound inlet microphone by placing an extra enclosure, or enclosures, in the attenuator for each additional sound inlet. For that alternate embodiment the capacitance computations would differ but would be easily calculable by a person skilled in the art.
[0116] In FIG. 8, the simplified impedance of the human sound system is represented by a capacitance (Cm) in series with a current source (Im). The acoustic load is represented by a radiation resistance (Rr), although it is not a true resistor. Between capacitors, inductors and resistors, resistors are the only element that removes energy from the system. Rr is more a contrivance to show that energy is transmitted away from the system because the sound pressure across Rr is dissipated into open space and as such, varies as 1/x2, where x is the distance from the mouth to the measurement point, here the attenuator/microphone assembly. In other words, Rr is not a true resistor since its value depends on frequency. Without a value of Rr that is independent of frequency, if we model the human voice system emanating from the mouth as a plane piston in an infinite baffle, according to Beranek (“Acoustics”, p. 124), the radiation resistor's value varies as ω2, or (2*π*f)4, up to some frequency where the wavelength is commensurate with the driver's size. For higher frequencies the acoustic resistance is comparatively flat, meaning sound pressure level for a constant value of Im will rise by 12 dB/octave=dB/decade.
[0117] FIG. 9 shows another electrical analog of the transfer of sound from its generation by the human mouth, to its transmission represented by an Acoustic Load, through the Attenuator, and then into a Microphone. FIG. 9 is comparable to FIG. 8, the difference being that resistor, Rr, has been replaced by a capacitor, Cload. Cload may preferably be a capacitor whose value is: Cload=Vload/(ρoc2). This value is the result of the formula for the capacitance of a volume. As a capacitor, its impedance will vary with frequency as 1/ω=1/(2*π*f). This suitably means that, for a constant electrical current, the signal should fall with frequency at a rate of 6 dB/octave=20 dB/decade.
[0118] FIG. 12 is a graph of frequency v. sound pressure level. The graph suitably compares actual measurements of the sound pressure level under different conditions as produced by the speaker for a horn driver, but without the horn itself. The size of the aperture of the speaker is 1.0″. This might be suitable for a head and torso simulator (HATS) if it were equalized to a flatter response. To avoid acoustic frequency artifacts specific to the speaker chosen, the data is normalized to the sound pressure level measured at 36″ for a free field. Therefore, the chart values for all frequencies in this data is set to 0 dB and has the reference number 1. The results can be compared for a free field measurement at 1″ (line 2), the SPL into a 2.4 cubic volume (line 3), and into a Quiet Phone (line 4) (a quiet phone is a product by Quiet inc. and is generally described by U.S. Pat. No. 8,948,411 (issued Feb. 3, 2015) and this document and its family of patents are incorporated by reference in their entirety). The Quiet Phone also has a 2.4 cubic inch chamber, but also has a side voice exhaust channel from the mouth to the ear. The final line (line 5) is for reference and shows a minus 40 dB/octave slope, matching the slope for line 3. In view of the foregoing discussion, it is possible to calculate the sound pressure level under these different conditions assuming the same driver level offset. For instance, at 100 Hz, when 50 SPL is measured at 36″ to the microphone, for the same drive level, 50+30=80 SPL will be measured at 1″. Accordingly, 50+86=136 dB SPL will be measured into a 2.4 cubic closed chamber, but only 50+56=106 dB SPL into the pickup.
[0119] If, however, we take into account a higher driver level so that 70 dB SPL average is recorded at 36″, but assume peak readings 15 dB higher, we get a maximum drive of 85 dB SPL. The numbers are then for each line at 100 Hz: =>85 dB SPL=>115 dB SPL=>171 dB SPL=>141 dB SPL. The side channel of the Quiet Phone does help, but an Acoustic Attenuator of 30 dB or more is obviously called for. With the Quiet Phone side channel and the attenuator, the level would be 141-30=111 dB, which is close to a conventional miniature microphone's limit. Without the side channel into the same enclosed volume, the level is 171−30=141 dB, resulting in severe distortion.
[0120] FIG. 11 shows a graph measuring attenuation of seven 30 dB acoustic attenuators. It would be preferred that the acoustic attenuator had a perfectly flat response over the entire acoustic band of 20 Hz to 20 kHz. As can be seen in FIG. 11, there are some limitations to the attenuators discussed so far. In general, for all of the microphone/attenuator combinations shown, the attenuation decreases at both the high and low frequencies, with greater change at high frequencies. The performance shown is completely adequate for speech quality and intelligibility, covering the range 200 Hz to 8 kHz, but this range can be improved.
[0121] The simplest improvement is electrical equalization. The shape of the attenuation does differ between the two microphone models, but for the examples of the particular model, the shapes are fairly constant, so an equalization network should give a consistent performance. It is true that the overload margin for the preamplifier is decreased, but the acoustic energy for speech is predominantly in the central portion of the curve and may not be a problem. However, there are methods to improve the shape of the attenuation curve that precede the microphone.
[0122] Returning to FIG. 10, the network showing the acoustical analogs, there are additional elements that occur in the mesh, beyond those shown of FIG. 8 or FIG. 9.
The ones that degrade performance are as follows:
Rdavt, the acoustic vent for the attenuator diaphragm;
Lda, the acoustic inductance leading to the attenuator diaphragm;
Rda, the resistive damping of air leading to the attenuator diaphragm;
Ldmic, the acoustic inductance leading to the microphone diaphragm;
Rdmic, the resistive damping of air leading to the microphone diaphragm; and,
Rdmicvt, the acoustic vent for the microphone diaphragm.
Suitably, the first three cause the attenuation reduction at the low and high frequencies.
Rdavt bypasses the attenuator diaphragm and should be as small as possible to have acoustic impedance as high as possible. Lda causes a peaking in the response shape within the pass band of the attenuator and should be as small as possible to shift the peak above the upper end of the pass band. Rda controls damping of the peak at the attenuator and should be set to flatten that peak. The last three can be set to minimize the attenuation's degradation, and the values need to be selected essentially are as in the preceding paragraph for the respective element. Unfortunately, the only way to do this is to design the microphone or select the microphone so that those criteria are met. Designing the microphone results in a more expensive microphone. Selecting the microphone is more cost efficient given the large number of microphone manufacturers, each with very broad product lines.
[0123] Returning to FIG. 11, the graph shows the results of applying the Acoustical Attenuator to seven microphones, four from one manufacturer and three from another. The first four from manufacturer A used the Acoustical Attenuator shown on FIGS. 5 & 6 (type D). The microphones' dimensions are 9.7 mm diameter and 5 mm length for a volume of 370 mm.sup.3. The last three use the same attenuator housing as on FIGS. 5 & 6 with the addition of the adaptor ring shown in FIG. 7 (type E), as the microphones from manufacturer B have smaller 6.0 mm diameters and 3.4 mm lengths mm for a volume of 96.1 mm.sup.3. The volume ratio is about 4:1 for external dimensions. As can be seen in the graph, microphones from manufacturer B seemed to be more uniform than manufacturer A's, but these were prototype assemblies made over a period of time using salvaged diaphragms. It is possible that some or all of the variations are due to problems caused by the salvage operation.
[0124] Returning again to FIG. 10, as noted earlier, the diaphragm for the acoustic attenuator (Cda) protects the microphone after attaching the acoustic attenuator. Both the attenuator 1 and microphone diaphragm 33 must be protected from damage during assembly. There are two problem concerns. The first is the attaching the acoustic attenuator to the microphone. It is possible to increase or decrease the attenuator's 1 pressure by orders of magnitude than any sound pressure level the microphone or the attenuator is normally exposed to by sliding the attenuator assembly forwards and backwards, respectively. It is also possible to expose both diaphragms to the vapors of the cements. Both effects may be minimized by providing a small relief hole in the attenuator 1, open while the cements are applied to the mating parts. This allows the pressure in the attenuator to equalize while the process is done, and the cement is cured. A small dab of cement can then be used to seal this vent.
[0125] The attenuator's level of attenuation can be checked before the microphone is cemented to the attenuator because the small leaks between the attenuator and the microphone will not affect the attenuation at or above 1 kHz when the vent hole is sealed with tape. The attenuator may be removed using its flange and replaced, even if the cement is strong enough to retain the microphone to the attenuator, although in a preferable embodiment the cement bond is breakable. When the bond is not breakable, a vent hole can be created in the attenuator's face and covered by tape while the assembly is checked and possibly replaced; as discussed, the tape sufficiently seals the vent hole to not affect attenuation. After the result is satisfactory, the vent hole can be covered over with a suitable viscous cement. Suitably, if the attenuator diaphragm is damaged after the assembly and after the vent hole is sealed, the diaphragm can be replaced by peeling back the viscous cement layer and replacing the diaphragm. Furthermore, the attenuator's volume can be ensured to be accurate if positive stops are used.
[0126] Additionally, adjusting the length of the chamber forming Cvol can also vary the attenuation. For example, in FIGS. 1 and 2 this could be achieved by sliding the microphone further in or further out of the sleeving. In FIG. 4, the walls forming Cvol could be telescoped back and forth to achieve the same effect; increasing the diameter of the chamber forming Cvol easily creates greater attenuation. Accordingly, FIG. 5 could be considered preferable to FIG. 4 because of FIG. 5's greater volume.
[0127] Furthermore, adjusting the attenuation also adjusts the microphone's sensitivity. The adjustment could be used to achieve better uniformity from microphone to microphone because the base microphones' sensitivity normally varies by +/−3 dB to +/−4 dB according to industry specifications. For multi-inlet microphones, especially directional and noise canceling microphones, it is necessary to provide an acoustic attenuator for each sound inlet. It is necessary that the attenuator does not alter the level or phase of the input signals presented at each sound inlet. This is possible to achieve by matching the attenuators as they are built and then testing them to ensure good amplitude and phase match; a selection process to form a matched set is reasonable.
[0128] FIGS. 13 and 14 show an improved housing for a microphone that is configured to reduce the plosive raw voice of regular or impaired speech. As shown in FIG. 14, the side channel of the quiet phone suitably includes a low durometer voice air flow flap for exhale speech and inhale life air intake as needed for plosive words require more air flow for pronunciation. Suitably, the area for voice air intake and exhaust may be always open for normal speech and air inhalation but closed off during expression of plosive words. In other words, the flap design provides an area for the flap to open both outwardly and inwardly (both ways) and, as a result, assists with sound containment in the voice capture area of the quiet phone. As shown in FIG. 13, a speaker's face is hermetically sealed by contact of the phone handset against the speaker's face. Suitably, the chamber features a hermetically sealed plosive energy screen to remove voice plosive air pressure during expression into the phone. Further shown in FIG. 13, an attenuator—30 dB substantially lowers peak to peak dB energy prior to electret microphone pickup and the attenuator is suitably surrounded by dense memory foam with slow rebound time and this further attenuates voice sounds as they attempt to escape the quiet phone. As a result, the microphone receives sounds with a lower peak to peak electrical signal that is not distorted.
[0129] FIGS. 16 and 17 depict a flow chart and diagram for assisting communication of an individual that has a speech disorder or impaired speech. As shown, a user may be shown an image and asked to describe what is seen in order to build a vocabulary of words representing the user's impaired vocabulary. Suitably, a database of the user's impaired speech and associated vocabulary is saved in a database such that when a user speaks impaired speech into the quiet phone, corrected robotic speech or else voice to text is output from the quite phone to a microphone or graphical user interface. As shown in FIG. 17 a user's raw voice may be provided into a chamber of a handset that produces even pressure of the voice (see FIGS. 13 and 14). Preferably, the chamber of the handset may include an attenuator and microphone as described above for picking up a nondistorted signal of the user's impaired speech. Suitably, a computerized speech recognition software application may thereafter be used to compare the input impaired speech to a database of impaired speech associated with correct vocabulary such that corrected robotic speech or else voice to text is output from the quite phone to a microphone or graphical user interface.
[0130] Although the method and apparatus is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead might be applied, alone or in various combinations, to one or more of the other embodiments of the disclosed method and apparatus, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the claimed invention should not be limited by any of the above-described embodiments.
[0131] Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open-ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like, the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof, the terms “a” or “an” should be read as meaning “at least one,” “one or more,” or the like, and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that might be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.
[0132] The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases might be absent.
[0133] Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives might be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration.
[0134] All original claims submitted with this specification are incorporated by reference in their entirety as if fully set forth herein.
