Vesper - Confidential
8
Signal Quality Check:
Part 1/3 - Measuring SNR
Steps to measure SNR:
1. Wear the TWS mockup. Make
two recordings
of the VA signal:
a) Silence Recording
: 10 seconds of silence
b) Speech Recording
: 10 seconds of speech (wearer is talking, e.g. reciting Harvard Sentences)
2. Bandpass
both recordings with a bandpass filter (120Hz - 2kHz, 30dB/octave)
3. Compute
the following:
a) Compute RMS of
Silence Recording
Noise,
RMS
noise
b) Compute RMS of
Speech Recording
Total Noise + Speech,
RMS
total
c) Calculate Voice RMS from previous two results
RMS
voice
= sqrt(
RMS
total
2
–
RMS
noise
2
)
d) Calculate SNR in dB
SNR
dB
= 20·log
10
(
RMS
voice
/
RMS
noise
)
In a good TWS mockup with normal voice loudness, measured SNR should be
>>6dB.
