Author Topic: Interaction of SoundMeter and "made for iPhone" hearing aids  (Read 1276 times)

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sbiggar

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Interaction of SoundMeter and "made for iPhone" hearing aids
« on: January 02, 2017, 12:47:52 PM »
I realize my request is not typical and is probably not a real issue but I'm not sure where else to ask.

I've got SoundMeter 8.4.3 (r1594) with the Octave Analyzer option installed on an iPhone 6 Plus running iOS 10.2.  I'm older and use hearing aids (moderate to severe high frequency loss) so I'm interested in sound levels in various environments (like my office with loud air handlers).  Recently I got new "made for iPhone" hearing aids from Oticon (Opn).  The aids connect to the phone using Bluetooth and cell phone calls are routed directly to the hearing aids but the internal iPhone microphone is used for transmitting sound for phone calls.  When the hearing aids are connected, the Octave analyzer will not run.  It issues a message in a white box:  Unsupported Sample Rate The selected input device operates at a sample rate which is not supported for octave band analysis.

The SoundMeter Meter part works fine using the "Bottom microphone" input with or without the hearing aids connected.

I assume that the hearing aid connection has set up the audio sampling hardware in a mode that is incompatible with the analyzer.

I wonder if an external calibrated mic with external A/D and electronics (iTestMic2 for example) would work correctly with SoundMeter and the analyzer option with my hearing aids connected to the phone?

Thanks,

Stuart

FaberAST

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Re: Interaction of SoundMeter and "made for iPhone" hearing aids
« Reply #1 on: January 05, 2017, 12:03:28 PM »
Stuart,

Bluetooth mic input is typically sampled at 8 kHz. The weighting filters in the Meter and the bandpass filters in the Octave analyzer are designed to operate at multiples of 44.1 kHz and 48 kHz, which would explain the "Unsupported Sample Rate" message.

It seems that some time ago Apple changed the behavior of Bluetooth audio in iOS (at least in the Measurement Mode that SoundMeter uses). Since SoundMeter requires both input and output from the audio system, Bluetooth won't work unless you are using a Bluetooth headset (or hearing aids, in your case) with both input and output. Unfortunately, if you use a headset for input and output, then the sample rate will be restricted to 8 kHz (for both input and output).

This is a change from how Bluetooth used to work on iOS, when it was possible to use the built-in mic with Bluetooth output.

I wish I had better news.

Ben