# SPL at the output of wireless earphones



## ak71vie (Nov 26, 2014)

The settings is an Android phone connected to earphones through Bluetooth. I need to know the SPL value at the headphone speaker as a function of the sound amplitude (pure-tone) in the Android phone. 

When the earphones are connected to the jack of the phone, the sound amplitude applied to the impedance of the headphone speaker results in a current. With that current and the sensitivity of the headphone speaker, I can approximate the SPL value. -- This techinque, however, does not apply to wireless transmission. Kindly ask to let me know how to proceed.

Your support is highly appreciated


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## AudiocRaver (Jun 6, 2012)

ak71vie said:


> The settings is an Android phone connected to earphones through Bluetooth. I need to know the SPL value at the headphone speaker as a function of the sound amplitude (pure-tone) in the Android phone.
> 
> When the earphones are connected to the jack of the phone, the sound amplitude applied to the impedance of the headphone speaker results in a current. With that current and the sensitivity of the headphone speaker, I can approximate the SPL value. -- This techinque, however, does not apply to wireless transmission. Kindly ask to let me know how to proceed.
> 
> Your support is highly appreciated


First, there are frequencies at which a headphone's frequency response (FR) vary a LOT. Any pure tone measurement will probably give you a big error, unless you are just plain lucky and pick the right tone, which is highly unlikely. A sensitivity number will probably involve pink noise.

With Bluetooth headphones, the sensitivity number will not be relative to a voltage or current, but to the full-scale signal, or to the level where you hear the signal just starting to clip.


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