Crop spectrum for analysis

[pcremades]

Dear Bill,
Firstly I want to thank you for this super useful app. I'm a physics teacher and I do open source hardware/free software for teaching. A few years ago I built a Kundt's tube to measure the speed of sound. Your Oscilloscope app came in handy because the spectrum lets me see the tone I'm generating inside the tube and measure the intensity, which helps finding the nodes of the standing wave.
The only limitation we have is that we have to make the experiment in a quiet place because if there is ambient noise, the decibelimeter in the app shows the global intensity and not that of the pure tone. I was wondering if it would be possible to add the option to crop the spectrum so that the decibelimeter measures only in a certain frequency range. We normally work with high frequencies, around 10kHz.

Kind regards,
Pablo

[billthefarmer]

I have an app for that, it runs on windows or mac – SLMS

[pcremades]

Thank you Bill. Unfortunately, the kundt's tube is designed to be used with 2 smartphones, because every student has one. I will try to add this functionality to Oscilloscope.

[billthefarmer]

You could calculate the fundamental level from the level and the harmonic distortion.