PROTECTING MICROPHONES FROM WIND NOISE PICKUP

PublishTime：2022-04-26

●Microphones are highly sensitive to wind noise, limiting their performance when used outdoors. A properly designed wind protector can significantly reduce thisnoise level. Mechanically reducing the wind noise enables further noise reduction using software, expands opportunities for using microphones. The design of the wind protection is not intuitively obvious, careful design is needed create protection that is both unobtrusive and effective. This document provides some recommended designs and the theory behind them.
●OVERVIEW
■As intelligent audio devices are becoming more portable, they are more likely to be used in windy situations. The microphones in electronic devices are more directly exposed to the wind than our eardrums, making them more sensitive to wind noise. Wind noise interferes with hearing other sounds, makingspeech harder to understand and environmental sounds harder to detect.
■Microphone booms have been used to improve the SNR by moving the microphone closer to the mouth. However, many users now want to have that same speech performance, without having an intrusive boom.
■Well-written software algorithms can reduce the perceived wind noise by more than 20 dB. However, these algorithms cannot do their job well if the speech to noise ratio (SNR) is already well below 0 dB before processing.
■A good wind screen gives the algorithms a much better signal to work with, improving SNR by as much as 30 dB. The noise reduction can be achieved with no degradation of speech, improving the effectiveness of speech recognition systems. A wind screen also improves the ratio of environmental sounds to wind noise, which is helpful for preserving environmental awareness. It is quite difficult (if not impossible) for an algorithm to reduce wind noise while preserving environmental sounds with their spatial cues.
■A good wind screen works not only by keeping wind from directly hitting the microphone diaphragm, but also by keeping the source of the wind noise farfrom the microphone. The main source of wind noise is the turbulent motion that occurs when the airflow is disturbed, such as by our bodies and our electronic devices. How to control and shape this turbulent airflow is often not intuitively obvious.
■The next couple figures help give an idea of the problem caused by wind noise. Figure 1shows the speech SNR for a simple headset with no wind protection. This was measured using the experimental headset shown next to the graph. The SNR calculation assumes a speech level of 65 dB at the ear. The SNR goes below -30 dB for when walking outdoors in a gentle breeze.

Brand of Product：	Knowles
Part#：
Product Category：	Microphones More
Application：	More
Data Type：	Application note & Design Guide More
Safety & Environment Standards：	More
Operating Temperature：	Please see the document for details
Qualification Grade：	More
Qualification Approval：	More
Package：
Language：	English Chinese Chinese and English Japanese
Date of Creation：	11/25/18
Version Number：	REVISION 1
Data Encoding：	AN29
Data Size：	957 KB

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