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principle of bone conduction-2

Bone conduction is a method of sound conduction, that is, by converting sound into mechanical vibrations of different frequencies, sound waves are transmitted through the human skull, bone labyrinth, inner ear lymph, Corti’s organ, auditory nerve, and auditory center, and the auditory nerve generates nerve impulses. , transmitted to the auditory center, after comprehensive analysis of the cerebral cortex, and finally “hear” the sound.

The mechanism of bone conduction hearing is described as the “cochlea compression” effect. The mechanical vibrations containing sound information are transmitted to the cochlea through the skull system, such as the skull, temporal bone, and bony labyrinth, and push the oval window of the cochlea to vibrate, which in turn pushes the reciprocating flow of lymph in the cochlea. Due to the asymmetric structure in the cochlea (mainly the asymmetric structure produced by the vestibular apparatus), the effect of lymph fluid on both sides of the basilar membrane is inconsistent during the flow process, resulting in the corresponding deformation of the basilar membrane in the cochlea, triggering the hearing on the basilar membrane. Neuroreceptors generate nerve impulses that trigger hearing.

Bone conduction headphones are used to receive calls, that is, to listen to sounds. Bone conduction speakers do not need to pass through the external auditory canal, tympanic membrane, tympanic cavity and other traditional air conduction transmission medium, the sound wave vibration signal converted by the electrical signal is directly transmitted to the auditory nerve through the temporal bone. The sound is restored, and the sound waves will not affect others because of the diffusion in the air.


PremiumPitch™ 1.0

Two sets of resonance systems are designed in the loudspeaker to widen the frequency response range of the loudspeaker and improve the sound quality. The medium and high frequency resonance system is formed by the voice coil and the bracket to realize the good output of the loudspeaker in the middle and high frequency bands; the low frequency resonance system is formed by the vibration transmission plate (reed) and the magnetic circuit to enhance the low frequency output capability of the loudspeaker.

PremiumPitch™ 1.0+

Three groups of resonance systems are designed in the loudspeaker to further widen the frequency response range of the loudspeaker and improve the sound quality. A high-frequency resonance system is formed by a voice coil and a bracket to achieve good output of the loudspeaker in the high frequency range; a low-frequency resonance system is formed by a vibration transmission sheet (reed) and a magnetic circuit to enhance the low-frequency output capability of the loudspeaker; The reed connecting the transducer and the shell) and the transducer assembly form a mid-low frequency resonance system, which further enhances the medium and low frequency output capability of the speaker.

Premium Pitch™ 2.0

That is, the Premium Pitch™ 2.0 technology also applied to OpenSwim, which uses the voice coil in the speaker, the reed and the ear hook of the earphone to form a triple compound vibration system. The three components are respectively responsible for the sound output of different frequency bands, which makes the three frequencies more balanced and improves the sound quality. From the perspective of vibration output frequency response, Aeropex with integrated technology has a flatter frequency response than Air without this technology, indicating that the three frequencies are more balanced; at the same time, it has higher output in the low frequency band, indicating that its The amount of low frequency and diving is more sufficient. This all makes it have better sound quality. In addition, the integrated technology adopts a fully enclosed shell design, which further improves the waterproof performance of the bone conduction earphones.

PremiumPitch™️ 2.0+

Premium pitch™ 2.0+, the pitch technology described. The vibration direction of the bone conduction speaker relative to the face is changed from vertical to inclined at an angle, and from hitting the face vertically to rubbing the face at a certain inclination angle, which can effectively reduce the vibration of the user. This is the 30-degree tilt technique.


The air conduction sound leakage of the bone conduction earphone comes from the vibration of the shell when the bone conduction speaker is working. Leak slayer™ technology reduces sound leakage by using an air-conducted sound that is out of phase with the sound leakage to interact with the sound leakage to achieve a sound anti-phase cancellation effect.

Aeropex optimizes the design of the shell shape and structural mechanical parameters of the bone conduction speaker, so that the phase of the air conduction sound leakage generated at different positions on the bone conduction speaker shell is opposite, and the sound leakage from different positions of the shell interacts to achieve sound leakage Inverts the effect of cancellation, thereby reducing sound leakage.

The shell of the bone conduction speaker adopts a fully enclosed form to ensure that the shell has a large rigidity. The air-conduction sound leakage generated by the two surfaces perpendicular to the vibration direction of the shell is opposite in a wide frequency band (the upper limit cut-off frequency is not less than 5kHz), so Realize the cancellation of sound leakage and reduce the effect of sound leakage.

As for why Leak 1 is in opposite phase to Leak 2. Simply put, when the device shell moves in the vibration direction, for example, moving to the left, the air on the left side of the shell will be squeezed, so that the air density and air pressure on the left side of the shell will increase, forming a compression zone; at the same time, the shell As the air on the right side moves away from the shell to the left, the density becomes smaller and the air pressure becomes smaller, forming a sparse area. The sound pressure corresponding to the compression area is in an increasing state, and the corresponding sound pressure in the sparse area is a decreasing state, that is, the air conduction sound pressure generated on both sides of the shell increases left and right decreases, and the phase of the sound pressure on both sides is opposite. Similarly, when the vibration direction of the casing moves to the right, the air conduction sound pressure on the left and right sides of the casing decreases from left to right and increases on the right, and the phase of the sound pressure on both sides is still opposite.

In the anechoic room, use Air and Aeropex to play the same audio files (white noise was used in the test), and under the condition of the same listening volume, measure the sound leakage of the three and analyze the frequency spectrum of the leakage sound. From the results of spectrum analysis, in most frequency bands, the sound leakage of Aeropex is smaller than the former, showing a better effect of reducing sound leakage.

High sensitivity technology

High-sensitivity technology can improve the energy conversion efficiency of bone conduction speakers, reduce energy consumption, and reduce the volume and weight of speakers. It is achieved by reducing the leakage of the magnetic field of the bone conduction speaker and enhancing the strength of the magnetic field.

In the bone conduction speaker, the voice coil is placed in the magnetic field constructed by the magnetic circuit. When the voice coil is fed with an electrical signal, under the action of the magnetic field, the voice coil generates an ampere force, which in turn pushes the bone conduction speaker to vibrate and produce sound. The stronger the magnetic field, the greater the ampere force generated by the voice coil and the louder the sound. The traditional magnetic circuit has a large amount of magnetic field leakage, resulting in a sparse magnetic induction curve at the voice coil and a weak magnetic field strength. The high-sensitivity technology uses the secondary magnet to suppress the leakage of the magnetic field, and concentrates the magnetic field energy at the voice coil position, so that the magnetic induction curve at the voice coil is dense and the magnetic field strength is enhanced.

Using high-sensitivity technology, it can achieve smaller speaker volume, stronger magnetic circuit magnetic field, and output larger sound. Make the bone conduction speaker smaller (the size of the Aeropex speaker is reduced by 30% compared to the Air), and the bone conduction earphone is lighter (the weight of the Aeropex is reduced by 4g to 26g compared to the Air).

Dual Silicon Microphone Noise Cancelling

Dual silicon microphone noise reduction, that is, the dual silicon microphone design is used to improve the signal-to-noise ratio and pickup sensitivity. It is equipped with a CVC algorithm to eliminate call echo and ambient noise, improve call quality, and realize high-definition voice call function.

The noise reduction level of the microphone can be tested by the 3quest test method, and the N-MOS indicator in the test result represents the noise reduction level of the microphone. Generally speaking, if the N-MOS index is greater than 2.3 points (out of 5 points), it meets the requirements of the 3GPP communication standard. After testing, the N-MOS indicators under the Aeropex 3quest test using dual silicon microphones are 2.72 (narrowband communication) and 3.05 (broadband communication), which obviously exceed the noise reduction requirements of communication standards.

The test results of OpenMove are used here for illustration; the chip and dual-mic architecture used by OpenMove are consistent with Aeropex, and the directivity effect of the microphone is consistent; the directivity of the microphone can be achieved by using the dual-microphone design combined with the CVC algorithm of the QCC3024 chip. That is to say, the microphone only collects the sound from the direction of the user’s mouth, and does not collect noise from other directions.

Post time: Jun-22-2022