Musical instrument tuning

Abstract

A digital tuner that determines a tuning target period; receives an audio signal from an instrument to be tuned; obtains a plurality of different segments of the audio signal starting at times that correspond to integer multiples of the target period; produces waveform samples from the segments; and displays of a succession of waveform segments at same display position using said segments so that the shape of the waveform appears to move on the display at a speed and direction directly dependent on a difference of a wave period of the audio signal to be tuned and the tuning target period.

Claims

1. A digital tuning method comprising: determining a tuning target period; receiving an audio signal from an instrument to be tuned; obtaining a plurality of different segments of the audio signal starting at times that correspond to integer multiples of the target period; producing waveform samples from the segments; and causing displaying of a succession of waveform segments at same display position using said segments so that the shape of the waveform appears to move on the display at a speed and direction directly dependent on a difference of a wave period of the audio signal to be tuned and the tuning target period.

2. A digital tuner comprising: a tuning period selector configured to determine a tuning target period; an input for receiving an audio signal from an instrument to be tuned; at least one processor configured to cause: obtaining a plurality of different segments of the audio signal starting at times that correspond to integer multiples of the target period; producing waveform samples from the segments; and causing displaying of a succession of waveform segments at same display position using said segments so that the shape of the waveform appears to move on the display at a speed and direction directly dependent on a difference of a wave period of the audio signal to be tuned and the tuning target period.

3. The digital tuner of claim 2, wherein the displaying of the succession of waveform segments employs a representation other than the time-domain acoustic waveform of the sound.

4. The digital tuner of claim 3, wherein the representation has time resolution higher than a rate at which the target periods are received.

5. The digital tuner of claim 2, wherein the tuning period selector comprises a user interface configured to receive the tuning target pitch from a user.

6. The digital tuner of claim 2, wherein the tuning period selector comprises a tuning period selection circuitry configured to perform an automatic selection of the target pitch.

7. The digital tuner of claim 2, wherein the length of the displayed waveform segments is proportional to the target period.

8. The digital tuner of claim 2, wherein waveform samples are formed by combining groups of segments.

9. The digital tuner of claim 2, wherein the successive waveform segments are presented as diagrams representing intra-wave amplitude as a function of time.

10. The digital tuner of claim 2, wherein the magnitude of the successive waveform samples is automatically scaled based on dynamically measuring the level of the sound.

11. The digital tuner of claim 2, wherein the at least one processor is configured to adjust the tuning target period depending on a difference between the wave period of the audio signal to be tuned and the tuning target period.

12. The digital tuner of claim 2, wherein the at least one processor is further configured to determine movement speed of the displayed waveform segments by computing the movement distance between successive waveform segments divided by the time difference between the respective waveform segment start times.

13. The digital tuner of claim 11, wherein the at least one processor is further configured to set the tuning target period back to the original value of the tuning target period when the difference between the wave period of the audio signal to be tuned and the tuning target period meets a given closeness criterion.

14. The digital tuner of claim 11, wherein the at least one processor is further configured to provide a quantifying indication of the movement speed to a user.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Some example embodiments will be described with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a time domain illustration of a musical sound over a plurality wave periods;

(3) FIG. 2 shows a schematic drawing of a system according to an embodiment;

(4) FIG. 3 illustrates in time domain shapes of a plurality of successive periodic waves of FIG. 1 drawn on top of each other for illustrating similarity of successive waveforms;

(5) FIG. 4 shows in time domain a musical sound with a too low pitch;

(6) FIG. 5 illustrates in time domain shapes of a plurality of successive periodic waves of FIG. 4 drawn on top of each other for illustrating similarity of successive waveforms;

(7) FIG. 6 shows in time domain a musical sound where the sound produced by the instrument has too high pitch;

(8) FIG. 7 illustrates in time domain shapes of a plurality of successive periodic waves of FIG. 6 drawn on top of each other;

(9) FIG. 8 schematically illustrates screen update matching of an embodiment;

(10) FIG. 9 shows a block diagram of a digital tuner according to an embodiment;

(11) FIG. 10 shows a flow chart illustrating operation of a digital tuner of a first example aspect; and

(12) FIG. 11 shows a flow chart illustrating operation of a digital tuner of a third example aspect.

DETAILED DESCRIPTION

(13) In the following description, like reference signs denote like elements or steps.

(14) FIG. 1 shows a schematic drawing of a system 100 according to an embodiment. The system 100 comprises an audio source 110 to be tuned, such as a string of a guitar or violin, or a singer. The system 110 further comprises a digital tuner 120. In some embodiments, the system 100 further comprises an automatic actuator 130 controllable by the digital tuner 120 for automatically tuning the audio source when the audio source is an instrument. In some embodiments, the system 100 further comprises an external display 140, an external speaker 150 or a haptic user interface device 160, for outputting information from the digital tuner 120 to a user 170 also drawn in FIG. 2.

(15) Some of the embodiments disclosed herein are based on that in order to find out whether a musical sound is higher or lower than a given target pitch, it is sufficient to visualize the sound itself to the user in a specific way. That provides the user sufficient information to decide if the sound is in tune or too low or too high, and allows her to tune the musical instrument accurately. In other words, the pitch of the sound does not need to be measured at all, but the user herself replaces a tuning measurement device common in present digital tuners by looking at the visualization and judging from that whether the sound is too low or too high, and by how much.

(16) Let us refer back to FIG. 1. Pitched musical sounds exhibit periodicity in their time-domain waveform 112. FIG. 1 illustrates a guitar sound with a pitch of 440 Hz and period-length of 1/440 Hz=2.27 ms. Vertical grid lines in FIG. 1 indicate multiples of the period length of the sound. As can be seen, the waveform from one period to the next is nearly identical. This is illustrated also in FIG. 3, where individual periods of the waveform 112 are overlaid on top of each other. Although the waveshape does not stay exactly the same, it changes very slowly: gradually morphing from one shape to another. Such pseudoperiodicity is characteristic to the sounds of pitched musical instruments.

(17) Let us now consider a situation where a tuning target pitch f.sub.TP (and therefore also a tuning target period length p.sub.TP) is given in advance. That is the situation when tuning a musical instrument: the correct tuning target pitch value f.sub.TP is given and the user 170 tries to adjust the musical instrument in order to produce a pitch that would match the tuning target pitch value f.sub.TP.

(18) FIG. 4 shows in time domain a musical sound where the sound produced by the instrument has too low pitch (“flat”) and therefore the waveform 112 has a period that is longer than the tuning target period p.sub.TP.

(19) FIG. 5 illustrates in time domain shapes of a plurality of successive periodic waves of FIG. 4 drawn on top of each other for illustrating similarity of successive waveforms 112. In this case, the waveform shape appears to moves right. In other words, the waveform shape does not remain horizontally stable, but the latest waveform segment is further to the right-hand direction than the earlier segments.

(20) FIG. 6 shows in time domain a musical sound where the sound produced by the instrument has too high pitch (“sharp”) and therefore the waveform 112 has a period that is shorter than the tuning target period p.sub.TP.

(21) FIG. 7 illustrates in time domain shapes of a plurality of successive periodic waves of FIG. 6 drawn on top of each other for illustrating similarity of successive waveforms 112. In this case, the waveform shape appears to moves left. In other words, the waveform shape does not remain horizontally stable, but the latest waveform segment is further to the left-hand direction than the earlier segments.

(22) In some embodiments, there is no need to measure or estimate the pitch of the produced musical sound in order to allow the user to tune the musical instrument. Instead, the musical sound is received and displayed in short segments so that subsequent segment of the musical sound are picked from a temporal position that is a multiple of the target tuning period p.sub.TP. When the sound is perfectly in tune, the display “stabilizes” horizontally as illustrated by FIG. 3. If the sound is slightly too low (“flat”), the image moves/scrolls towards right (see FIG. 5), which indicates to the user that she should tune the pitch higher. Movement to the opposite direction (see FIG. 7) indicates that the pitch is too high.

(23) In practice, the frame-rate of the display device may not match the pitch of the sound: the interval between screen updates (for example 60 frames per second) is usually different from the rate at which we receive periods of the sound waveform 112 (for example 440 times per second). Various embodiments improve compatibility of the display device with the pitch of the sound for further smoothing the presentation whereas some embodiments simply display with the frame rate of the display. For example, one embodiment always draws the latest received segment of the audio waveform 112 that starts at a multiple of target period T and has been fully received before the screen update.

(24) FIG. 8 schematically illustrates screen update matching of an embodiment. In FIG. 8, the screen update interval is 2.5 times longer than the time interval between successive tuning target periods p.sub.TP. In FIG. 8, rectangles are drawn to indicate latest received complete segment or tuning target period before each screen update. In this case, every second or third wave is displayed. Another embodiment displays all the fully-received periods that have arrived between two screen updates, or a fixed number of latest periods. Yet another embodiment calculates a point-by-point average of all the segments or a fixed number of the segments that have arrived since the previous screen update and displays the average waveshape.

(25) FIG. 9 shows a block diagram of a digital tuner 120 according to an embodiment. The digital tuner 120 comprises a memory 920 including a non-volatile memory 922 configured to store computer program code 930. The digital tuner 120 further comprises a processor 910 for controlling the operation of the digital tuner 120 using the computer program code 930, a work memory 924 for running the computer program code 304 by the processor 301, an input (or input/output) unit 960 for receiving audio signals and optionally communicating to other entities such as the actuator 130. The processor 301 may be a master control unit (MCU). Alternatively, the processor may be a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array, a microcontroller or a combination of such elements. In some embodiments, the digital tuner is a remote device accessible by radio or through a communication network, such as the Internet. Particularly in that case, the hardware of the digital tuner may be virtualized or similar functions may be provided through cloud computing. The digital tuner 120 further comprises a user interface 960 for displaying and/or presenting acoustic information to the user 170.

(26) FIG. 10 shows a flow chart illustrating operation of a digital tuner of a first example aspect, comprising:

(27) 1010. determining a tuning target period;

(28) 1020. receiving an audio signal from an instrument to be tuned;

(29) 1030. obtaining a plurality of different segments of the audio signal starting that correspond to different integer multiples of the target period;

(30) 1040. producing waveform samples from the segments; and

(31) 1050. causing displaying a succession of waveform samples at same display position so that the shape of the waveform samples appears to move on the display at a speed and direction directly dependent on a difference of a wave period of the audio signal to be tuned and the tuning target period.

(32) In an embodiment, the displaying 13 ∧length of the succession of waveform segments employs a representation other than the time-domain acoustic waveform of the sound.

(33) The representation has time resolution higher than a rate at which the target periods are received so that there are several successive time-points in the representation within each individual target period.

(34) In an embodiment, the representation comprises filtered versions of the acoustic waveform 112. For example, filtered versions may be produced using any of lowpass, highpass, and/or bandpass filtering.

(35) In an embodiment, the representation comprise a power envelope of the acoustic waveform 112, which power envelope can be obtained, for example, by squaring each sample value of the sound waveform 112 and optionally applying filtering such as low-pass filtering on the squared signal.

(36) In an embodiment, the representation comprises a time-frequency spectrogram of the input signal. The spectrogram has time resolution that high that the distance between successive spectra (“frames”) in the spectrogram is shorter than the target period T. The spectrogram is based on several different frequency magnitudes at each of a plurality of time points to describe the spectrum of the sound at those points. To this end, the spectrogram can be displayed as an image with different colors or shades of gray representing the numerical values at different time-frequency positions or as a three-dimensional chart.

(37) FIG. 11 shows a flow chart illustrating operation of a digital tuner of a third example aspect, comprising:

(38) 1110. determining a tuning target period;

(39) 1120. receiving an audio signal of an instrument to be tuned;

(40) 1130. sampling the audio signal; and

(41) 1140. producing a combination signal for employing wave interference by adding an inversed first waveform segment corresponding to an earlier portion of the received audio signal to a second waveform segment corresponding to a subsequent portion of the audio signal;
1150. wherein the first segment and the second segment are based on portions of the audio signal starting with at different integer multiples M of tuning target period T, wherein M is an integer greater than or equal to zero; and
1160. outputting the combination signal in order to indicate tuning of the audio signal.

(42) Various embodiments have been presented. It should be appreciated that in this document, words comprise, include and contain are each used as open-ended expressions with no intended exclusivity.

(43) The proposed aspects of the disclosed embodiments are based on an idea that bears some resemblance to the above-described analog rotating-disc strobe tuner. However there are also clear differences that set the aspects of the disclosed embodiments apart from prior art: 1) tuning is made using only the sound, without needing the rotating disc and 2) the sound itself is shown to the user in a way that provides the user sufficient information for accurate tuning. In other words, the pitch of the sound does not necessarily need to be measured at all, but the user is able to judge from the visualization directly whether the sound is too low or too high, and by how much.

(44) The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments a full and informative description of the best mode presently contemplated by the inventors for carrying out the aspects of the disclosed embodiments. It is however clear to a person skilled in the art that the present disclosure is not restricted to details of the embodiments presented in the foregoing, but that it can be implemented in other embodiments using equivalent means or in different combinations of embodiments without deviating from the characteristics of the present disclosure.

(45) Furthermore, some of the features of the afore-disclosed embodiments of the present disclosure may be used to advantage without the corresponding use of other features. As such, the foregoing description shall be considered as merely illustrative of the principles of the present disclosure, and not in limitation thereof. Hence, the scope of the present disclosure is only restricted by the appended patent claims.