Acoustic vs Electrical audio measurement

[Acoustic]
1. Rx
The Rx voice/sound is output from the speaker on the mobile phone and received by the artificial ear.
The artificial ear received signal is then input to ADC in HATS and then sent into the equipment for analysis.



2. Tx
The voice/sound is output from the artificial mouth and received by the mic on the mobile phone.
The received voice/sound is then input to ADC in the mobile phone and then do the successive processing.
Then the processed signal is sent by radio into the call box and the equipment for analysis.



[Electrical]
1. Rx
The Rx signal is not played by the speaker on the mobile phone.
The Rx output signal is measured at MSM output pin directly (ex. HPH pin for headset).



2. Tx
The Tx signal is sent into MSM via mic input pin directly (ex. MIC1 pin for handset).






Shortly speaking, only in the acoustic test, the voice/sound will be played out.
In electrical test, the signal is sent or received directly at the input or output pin on MSM.



One common question from the customer:
Why is the frequency response of the speaker is flat in the speaker standalone test, but after the speaker being connected onto MSM, the overall Rx frequency response is not flat when measuring by ACQUA?
This is because in the speaker standalone test, the frequency response is measured electrically, but the overall Rx frequency response is measured by ACQUA acoustically.
Since the method of measurement is different, the result cannot be compared.
The correct way is to test the overall Rx frequency response electrically as well for the comparison.