The sound level in the app is negative and when measurement the spectrum starts from about -125 db ?
What dose that mean?Why like other spectrum analyzers is not referencing from 0 db ?
The db measurement is a relative measurement not an absolute measurement. 0db is when the signal completely saturates the microphone input. The way to reference it to 0db (SPL) for an absolute measurement would be to characterize every different phone’s microphones over the whole frequency range. Other analyzers or SPL apps might do that for some phones, or just might be taking a wild guess. For a rough measurement you could measure the sound of a sine wave in a SPL app or device and offset the peak in the spectrum analyze app to be at that same value. So if a 60dbSPL measured sinewave in a SPL device was -70db peak on the app. Then you the -70db measurement is at 60dbSPL and you offset all the frequencies based on that. Such as another peak at -60db is 50dbSPL.
The sound level in the app is negative and when measurement the spectrum starts from about -125 db ?
What dose that mean?Why like other spectrum analyzers is not referencing from 0 db ?
The db measurement is a relative measurement not an absolute measurement. 0db is when the signal completely saturates the microphone input. The way to reference it to 0db (SPL) for an absolute measurement would be to characterize every different phone’s microphones over the whole frequency range. Other analyzers or SPL apps might do that for some phones, or just might be taking a wild guess. For a rough measurement you could measure the sound of a sine wave in a SPL app or device and offset the peak in the spectrum analyze app to be at that same value. So if a 60dbSPL measured sinewave in a SPL device was -70db peak on the app. Then you the -70db measurement is at 60dbSPL and you offset all the frequencies based on that. Such as another peak at -60db is 50dbSPL.
Bryce