Audio can be processed only on the edge or device side. In addition, drilling holes for secondary mics poses an industrial ID quality and yield problem. Multi-mic designs make the audio path complicated, requiring more hardware and more code. They require a certain form factor, making them only applicable to certain use cases such as phones or headsets with sticky mics (designed for call centers or in-ear monitors). Multi-microphone designs have a few important shortcomings. Moving from Multi-microphone design to Single-microphone In most of these situations, there is no viable solution. Users talk to their devices from different angles and from different distances. Wearables (smart watches, mic on your chest), laptops, tablets, and and smart voice assistants such as Alexa subvert the flat, candy-bar phone form factor. However the “candy bar” form factor of modern phones may not be around for the long term. Necessary form factor for noise cancellation when using multi-mic arrays When the user places the phone on their ear and mouth to talk, it works well.įigure 3. The distance between the first and second mics must meet a minimum requirement. The form factor comes into play when using separated microphones, as you can see in figure 3. Existing noise suppression solutions are not perfect but do provide an improved user experience. Given these difficulties, mobile phones today perform somewhat well in moderately noisy environments. Audio/Hardware/Software engineers have to implement suboptimal tradeoffs to support both the industrial design and voice quality requirements… Two and more mics also make the audio path and acoustic design quite difficult and expensive for device OEMs and ODMs. Or imagine that the person is actively shaking/turning the phone while they speak, as when running. Imagine when the person doesn’t speak and all the mics get is noise. This sounds easy but many situations exist where this tech fails. #Outdoor white noise machine software
Software effectively subtracts these from each other, yielding an (almost) clean Voice.
The mic closer to the mouth captures more voice energy the second one captures less voice. The two mics are marked yellowīoth mics capture the surrounding sounds. Phone designers place the second mic as far as possible from the first mic, usually on the top back of the phone.įigure 2. The first mic is placed in the front bottom of the phone closest to the user’s mouth while speaking, directly capturing the user’s voice. This remains the case with some mobile phones however more modern phones come equipped with multiple microphones (mic) which help suppress environmental noise when talking.Ĭurrent-generation phones include two or more mics, as shown in figure 2, and the latest iPhones have 4. The mobile phone calling experience was quite bad 10 years ago. Once captured, the device filters the noise out and sends the result to the other end of the call. This seems like an intuitive approach since it’s the edge device that captures the user’s voice in the first place. Traditional noise suppression has been effectively implemented on the edge device - phones, laptops, conferencing systems, etc. Traditional Approach to Noise Suppression This post focuses on Noise Suppression, not Active Noise Cancellation. Active noise cancellation typically requires multi-microphone headphones (such as Bose QuiteComfort), as you can see in figure 2. This contrasts with Active Noise Cancellation (ANC), which refers to suppressing unwanted noise coming to your ears from the surrounding environment. Noise Suppression filters it out for both callers.
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