Hello, all --- Welcoming myself to the list here. I'm currently contributing to the PortAudio library and developing two audio-centric applications for OS X, one of which is a pro audio app which performs real-time voice pitch analysis.
Both of the applications I'm developing perform measurements of the user's voice, often analyzing long, sustained tones. Noise reduction algorithms including Apple's own interfere with this process by attenuating the user's voice after about a second, giving us inaccurate SNR and power measurements. Assuming it is not possible to bypass the effect, I would like to make a best effort at detecting "Ambient Noise Reduction" on input devices, so I can recommend my users to disable it. I have not identified any queries within the Core Audio API which reveal this state --- is there any way to retrieve it within a native application? If it's not accessible, the next best thing would be to determine whether the input device is one that supports the setting. Is there a standard list of device names or IDs that govern whether the setting is available? A sidenote that deserves mention: I'm running Mac OS 10.10.5 on a MacBook Air, and *disabling the Ambient Noise Reduction setting has no effect*: I observe the same gradual attenuation of a sustained tone between 4 and 8 seconds after onset. I assume this is a bug in the operating system and it's likely to cause trouble for my users. – Evan Balster creator of imitone <http://imitone.com>
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