Active noise cancellation device and earphone having acoustic filter

Abstract

An active noise cancellation device having an acoustic filter includes: a casing, an active noise cancellation unit, a speaker, a noise cancellation processor and an acoustic filter. The casing includes a first channel and a second channel, wherein a channel length of the first channel is greater than a channel length of the second channel. The active noise cancellation unit includes an external microphone disposed outside the casing. The active noise cancellation is configured to detect an ambient noise, wherein a location of the external microphone corresponds to a location of the first external end of the first channel. The speaker is disposed at a second external end of the second channel, and is configured to output a phase-inverted signal of the ambient noise. The noise cancellation processor electrically couples with the external microphone and the speaker. The acoustic filter is disposed inside the first channel.

Description

BACKGROUNDTechnical Field[0001]The present invention relates to a noise cancellation device, and in particular, to an active noise cancellation device, a circumaural earphone, and an in-ear earphone.Related Art[0002]According to a most common conventional noise suppression technology, noise suppression is implemented in most cases by passively absorbing noise energy by using various sound absorption materials. However, in a low frequency status, a wavelength of a sound is far greater than a thickness of a general sound absorption material. For example, a sound whose frequency is 100 Hz has a wavelength about 3.4 meters at sea level and under the normal atmospheric temperature. Therefore, transmission of a low frequency sound can be effectively blocked only by using a very thick and heavy sound absorption material. However, for general application, this passive noise cancellation technology is not ideal for a capability of isolating a low-frequency noise. Therefore, during practical ...

AI Technical Summary

Benefits of technology

The active noise cancellation device combines the active noise cancellation unit and the acoustic filter to form a band pass filter. This results in a sound in a particular frequency domain passing through the device to enter the listener's auditory canal. The device reduces noise intensity in the lower frequency channels and enhances noise cancellation in the higher frequency channels.

Problems solved by technology

However, for general application, this passive noise cancellation technology is not ideal for a capability of isolating a low-frequency noise.

Therefore, during practical application, according to a passive noise cancellation method, a balance often needs to be achieved in a problem of contradiction between effective cancellation of a low-frequency noise and a sound absorption material, wherein the sound absorption material may occupy very large space and have a large size and a high cost.

However, a main noise cancellation range of the general active noise cancellation earphone is a medium and low frequency range of 50 Hz to 2 KHz, and a reduction effect for a high frequency noise is not good.

The cost is high for the protecting a general explosive sound is implemented through high-speed digital signal processing in circuit designs.

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