Hello,
I have a CSR8675 board that I am using for an audio experiment.
I have connected the output from the Signal generator directly to the input line of the CSR8675 board. The output from the CSR8675 board is a Knowles speaker that outputs audio sound. This audio sound is picked up a B&K (Bruel & Kjaer) microphone. The B&K microphone is connected to a signal conditioner, which in turn is connected to an Oscilloscope. I want to find the dB SPL of the voltage value of the signal from the signal generator.
The sensitivity of the B&K microphone is
Open-circuit Sensitivity (250 Hz)a: 50 mV/Pa, -26 dB ±1.5 dB re 1 V/Pa
So now for a V1rms (= V1pp x 0.3535) at the Signal generator, with 20 dB amplification at the signal conditioner. I'm assuming to calculate the dB SPL the formula is as follows.
( Since the B&K microphone has a sensitivity of -26dB, that equates to 0.05012V or 50 mV. )
A = 20 *log10 (V2rms/0.05012)
Where V2rms = Peak-to-Peak voltage level at the oscillator * 0.3535.
dB SPL = A - 26 + 94 - 20
**26 because of the B&K microphone
94 because of the 1 pa = 94 dB SPL
20 because thats the amplification I'm applying at signal conditioner.
The ref voltage for the sensitivity value of the B&K microphone is 1 Vrms/Pa. if I set the V1rms value to 1.0 at the signal generator, then the dB SPL value calculated based on V2rms on the oscilloscope would indicate a dB SPL corresponding to that V1rms value. For example, let us assume,
V1rms of 1.0 gives a 70 dB SPL value based on the above calculation.
I would like to generate sounds from 40-100 dB SPL in 5 dB increments. So using the above calculation.
if I lower or increase V1rms, I can generate all the dB SPL sounds that I want.
Are my calculations correct or is there anything wrong with my setup ?
I have a CSR8675 board that I am using for an audio experiment.
I have connected the output from the Signal generator directly to the input line of the CSR8675 board. The output from the CSR8675 board is a Knowles speaker that outputs audio sound. This audio sound is picked up a B&K (Bruel & Kjaer) microphone. The B&K microphone is connected to a signal conditioner, which in turn is connected to an Oscilloscope. I want to find the dB SPL of the voltage value of the signal from the signal generator.
The sensitivity of the B&K microphone is
Open-circuit Sensitivity (250 Hz)a: 50 mV/Pa, -26 dB ±1.5 dB re 1 V/Pa
So now for a V1rms (= V1pp x 0.3535) at the Signal generator, with 20 dB amplification at the signal conditioner. I'm assuming to calculate the dB SPL the formula is as follows.
( Since the B&K microphone has a sensitivity of -26dB, that equates to 0.05012V or 50 mV. )
A = 20 *log10 (V2rms/0.05012)
Where V2rms = Peak-to-Peak voltage level at the oscillator * 0.3535.
dB SPL = A - 26 + 94 - 20
**26 because of the B&K microphone
94 because of the 1 pa = 94 dB SPL
20 because thats the amplification I'm applying at signal conditioner.
The ref voltage for the sensitivity value of the B&K microphone is 1 Vrms/Pa. if I set the V1rms value to 1.0 at the signal generator, then the dB SPL value calculated based on V2rms on the oscilloscope would indicate a dB SPL corresponding to that V1rms value. For example, let us assume,
V1rms of 1.0 gives a 70 dB SPL value based on the above calculation.
I would like to generate sounds from 40-100 dB SPL in 5 dB increments. So using the above calculation.
if I lower or increase V1rms, I can generate all the dB SPL sounds that I want.
Are my calculations correct or is there anything wrong with my setup ?
