Audio channels on videoconferencing systems usually process the audio signal to reduce background noise. These noise reduction algorithms are designed specifically for voice processing, detecting human voice and treating any other sound as noise to be suppressed. If stethoscope sounds are transmitted via such audio channels, the heart or lung sounds are suppressed as noise.
In order to transmit stethoscope sounds, it is necessary to disable noise reduction on an audio channel, so that the stethoscope sound is transmitted without any modification.
Thinklabs has worked with some commercial videoconferencing platforms to offer a means to disable noise reduction when switching from the patient side voice microphone to the stethoscope.
When implementing a custom videoconferencing system based on WebRTC, it is necessary to provide the same control of noise reduction, ideally enabling it during voice communication from the patient side, and disabling it when transmitting stethoscope audio from the patient side.
Some WebRTC services provide the means to control noise reduction, while others may not. You should check with your WebRTC provider to ensure that (a) there is a method to enable/disable noise reduction and (b) that this feature is available on all the platforms you intend to use (PC, Mac, iOS, Android etc) and the browser you will use. Sometimes the feature is only offered on PC/Mac.
When implementing the clean/unfiltered stethoscope channel, some of our customers control noise reduction (on/off) on a single channel when switching between voice and stethoscope, while others have implemented two separate parallel channels - a voice channel with noise reduction and a stethoscope audio channel without noise reduction.
When you implement your WebRTC solution, if the stethoscope sound begins to fade over time (within 10 seconds), this is usually an indication that a noise reduction algorithm is gradually suppressing the stethoscope sounds as noise. If the stethoscope sound is consistent, and similar to the sound directly from the stethoscope, the channel is probably not performing noise reduction. It is critically important to have a clinician listen to your channel to confirm sound quality, or contact us and we can listen to your stethoscope channel quality.
Note that the above discussion only applies to audio from patient side to provider. The provider's voice channel does not need any modification and noise reduction of the provider's voice channel is beneficial. It is also important to provide for provider to patient communication while the stethoscope is being used, so that the provider can guide the patient while listening to heart and lung sounds.