The present disclosure provides a microphone including at least one acoustoelectric transducer and an acoustic structure. The acoustoelectric transducer is configured to convert a sound signal to an electrical signal. The acoustic structure includes a sound guiding tube and an acoustic cavity. The acoustic cavity is in acoustic communication with the acoustoelectric transducer, and is in acoustic communication with outside of the microphone through the sound guiding tube. The acoustic structure has a first resonance frequency, the acoustoelectric transducer has a second resonance frequency, and an absolute value of a difference between the first resonance frequency and the second resonance frequency is not less than 100 Hz. By disposing different acoustic structures, resonance peaks in different frequency ranges may be added to the microphone, which improves a sensitivity of the microphone near multiple resonance peaks, thereby improving a sensitivity of the microphone in the entire wide frequency band.

In an embodiment, a system for detection of trains at railroad crossings is provided. The system comprises a field-deployed detection and reporting device comprising a microphone, a communication module, a microprocessor, and an application. When executed on the microprocessor, the application receives data describing sounds captured by the microphone and identifies frequencies of a first received sound. The application also transmits, based on the identified frequencies and a formula, a first message via the communication module. The first received sound is generated by a warning bell sounded at the railroad crossing. The first message is received by a backend server that issues a first broadcast based on receipt of the first message. The application further determines that the first received sound discontinues. Based on the determination, the application sends a second message via the module to the backend server which issues a second broadcast that the crossing is reopened.

Provided are, among other things, systems, methods and techniques for processing an audio signal to add virtual bass. In one representative embodiment, an apparatus includes: (a) an input line that inputs an original audio signal; (b) a bass extraction filter that extracts a bass portion of such original audio signal; (c) an estimator that estimates a fundamental frequency of a bass sound within such bass portion; (d) a frequency translator that shifts the bass portion by a positive frequency increment that is an integer multiple of the fundamental frequency estimated by the estimator, thereby providing a virtual bass signal; (f) an adder having (i) inputs coupled to the original audio signal and to the virtual bass signal and (ii) an output; and (g) an audio output device coupled to the output of the adder.

Provided are, among other things, systems, methods and techniques for processing an audio signal to add virtual bass. In one representative embodiment, an apparatus includes: (a) an input line that inputs an original audio signal; (b) a bass extraction filter that extracts a bass portion of such original audio signal; (c) an estimator that estimates a fundamental frequency of a bass sound within such bass portion; (d) a frequency translator that shifts the bass portion by a positive frequency increment that is an integer multiple of the fundamental frequency estimated by the estimator, thereby providing a virtual bass signal; (f) an adder having (i) inputs coupled to the original audio signal and to the virtual bass signal and (ii) an output; and (g) an audio output device coupled to the output of the adder.

The present disclosure discloses an acoustic output apparatus including at least one acoustic driver, a controller, and a supporting structure. The at least one acoustic driver may be configured to output sounds through at least two sound guiding holes. The at least two sound guiding holes may include a first sound guiding hole and a second sound guiding hole. The controller may be configured to control a phase and an amplitude of the sounds generated by the at least one acoustic driver using a control signal such that the sounds output by the at least one acoustic driver through the first and second sound guiding holes have opposite phases. The supporting structure may be provided with a baffle and configured to support the at least one acoustic driver such that the first and second sound guiding holes are located on both sides of the baffle.

The present disclosure discloses an acoustic output apparatus including at least one acoustic driver, a controller, and a supporting structure. The at least one acoustic driver may be configured to output sounds through at least two sound guiding holes. The at least two sound guiding holes may include a first sound guiding hole and a second sound guiding hole. The controller may be configured to control a phase and an amplitude of the sounds generated by the at least one acoustic driver using a control signal such that the sounds output by the at least one acoustic driver through the first and second sound guiding holes have opposite phases. The supporting structure may be provided with a baffle and configured to support the at least one acoustic driver such that the first and second sound guiding holes are located on both sides of the baffle.

A speaker system includes a first driver unit, a second driver unit and a cylinder case. The first driver unit and the second driver unit are disposed face to face with the same axial line. The axial line of the first driver unit and the axial line of the second driver unit forms a coaxial axial line or parallel axial lines. The cylinder case is hollow. The first driver unit and the second driver unit are disposed inside the cylinder case and contacts the inner wall of the cylinder case so that the central axial line of the cylinder case is parallel to the coaxial axial line or the parallel axial lines. A speak device includes a plurality of speaker systems. By the aforementioned configuration, even driver units may be disposed in a common cavity.

A headphone includes: a housing including a first aperture; a first driver unit disposed in the housing; a partition wall dividing an internal space of the housing into a first space and a second space, the first space communicating with an external space through the first aperture and containing the first driver unit; and a second driver unit attached to the partition wall.

A specialized audio/instrument cable with built-in digital signal processing capabilities that adds digital audio sampling capabilities that allows the user to trigger synthesized sounds or virtual musical instruments from within the cable itself to affect the sound generated from an instrument or microphone such that the cable is the only connection needed between the instrument or microphone and an output device. Using voice recognition, the specialized cable can select an audio effects chain algorithm and/or sampled sound algorithm extrapolated from a musical digital audio fingerprint (MDAF) created from a desired musician's instrument to alter the sound of the input instrument's audio.

A specialized audio/instrument cable with built-in digital signal processing capabilities that adds digital audio sampling capabilities that allows the user to trigger synthesized sounds or virtual musical instruments from within the cable itself to affect the sound generated from an instrument or microphone such that the cable is the only connection needed between the instrument or microphone and an output device. Using voice recognition, the specialized cable can select an audio effects chain algorithm and/or sampled sound algorithm extrapolated from a musical digital audio fingerprint (MDAF) created from a desired musician's instrument to alter the sound of the input instrument's audio.