How to

To convert your stethoscope into a digital one, you will need these items:

• An electret microphone (e.g. collar mic: Flipkart, Amazon)
• Android based smartphone
• Bluetooth headphones with good bass.

To assemble the device follow these instructions:

• Select an earpiece for the stethoscope which has a large opening such that it can fit the microphone
• Remove the foam windscreen from the microphone. 
• Fit the microphone into the earpiece, ensure a snug fit.

• Plug the jack from the microphone into the smartphone.  

• Download the DIY stethoscope app from Google Play Store.
• Pair your headphones to the smartphone.
• Open the app and press Start 
• Hold the chest piece gently over the chest to auscultate

App Settings:

Mode

The app features two different modes: "General" and "Cardiac".

"General" mode is good for pulmonary auscultation, heart sounds are heard in this mode, but these are much better appreciated in the "Cardiac" mode. 

The "Cardiac" mode uses separate filters to reduce the noise and provides you with the detailed cardiac sounds similar to that of your traditional stethoscope.

Noise Reduction 

The app has 4 independent noise reduction processes working in the background. The 5th process provides you with 3 modes: "None", Pre-recorded Noise" and " Adaptive Noise". 

In "None" mode, the 5th process is turned off and this is the default setting. 

In the " Pre-Recorded Noise" mode, the app tries to cancel out the background static, noise of fans, air conditioners from the audio output. 

The "Adaptive Noise" mode lets you record a sample of your ambient sound and then cancels that from the audio output.. 

Intensity of noise cancelling by the 5th process can be modulated by the Noise Reduction slider. However, too strong noise reduction can interfere with sounds of clinical interest and sometimes lead to artefacts difficult to differentiate from crepitations, so always start with the lowest possible setting and work your way up. 

While recording the noise sample for "Adaptive Noise" care must be taken that someone must not be speaking in the background, as speech is very similar to breath sounds, and the app tends to cancel out the breath sound if the noise sample contains speech.