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Topic: Noise Floor (Read 1655 times) previous topic - next topic
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Noise Floor

I'm trying to ascertain the noise floor of my recording space. I set up my levels to what I would normally use to record acoustic guitar so it that peaks at around -6dbfs. Then I recorded "silence". Cooledit gives the figures below from its Statistical Info tool. So what's my noise floor - the Peak Amplitude figure, the Average RMS Power figure, something else?

   Mono
Min Sample Value:   -51
Max Sample Value:   55
Peak Amplitude:   -55.42 dB
Possibly Clipped:   0
DC Offset:   -.002
Minimum RMS Power:   -80.12 dB
Maximum RMS Power:   -71.2 dB
Average RMS Power:   -77.74 dB
Total RMS Power:   -77.59 dB
Actual Bit Depth:   16 Bits

Using RMS Window of 50 ms

Noise Floor

Reply #1 –
Quote from: botface on
I'm trying to ascertain the noise floor of my recording space. I set up my levels to what I would normally use to record acoustic guitar so it that peaks at around -6dbfs. Then I recorded "silence". Cooledit gives the figures below from its Statistical Info tool. So what's my noise floor - the Peak Amplitude figure, the Average RMS Power figure, something else?

   Mono
Min Sample Value:   -51
Max Sample Value:   55
Peak Amplitude:   -55.42 dB
Possibly Clipped:   0
DC Offset:   -.002
Minimum RMS Power:   -80.12 dB
Maximum RMS Power:   -71.2 dB
Average RMS Power:   -77.74 dB
Total RMS Power:   -77.59 dB
Actual Bit Depth:   16 Bits

Using RMS Window of 50 ms


In order to measure SPL you need some kind of acoustically calibrated device, or an acoustical calibrator to calibrate the mic, preamp, and analytical software that you have.

Measurements of noise only make sense when they are taken over a defined bandwidth.

Noise Floor

Reply #2 –
Quote from: Arnold B. Krueger on
Quote from: botface on
I'm trying to ascertain the noise floor of my recording space. I set up my levels to what I would normally use to record acoustic guitar so it that peaks at around -6dbfs. Then I recorded "silence". Cooledit gives the figures below from its Statistical Info tool. So what's my noise floor - the Peak Amplitude figure, the Average RMS Power figure, something else?

   Mono
Min Sample Value:   -51
Max Sample Value:   55
Peak Amplitude:   -55.42 dB
Possibly Clipped:   0
DC Offset:   -.002
Minimum RMS Power:   -80.12 dB
Maximum RMS Power:   -71.2 dB
Average RMS Power:   -77.74 dB
Total RMS Power:   -77.59 dB
Actual Bit Depth:   16 Bits

Using RMS Window of 50 ms


In order to measure SPL you need some kind of acoustically calibrated device, or an acoustical calibrator to calibrate the mic, preamp, and analytical software that you have.

Measurements of noise only make sense when they are taken over a defined bandwidth.

Sorry, badly worded question. I'm not trying to measure the ambient noise level of the room, I'm trying to get a feel for the noise content relative to a healthy signal of a typical recording made in that room. So, it would include noise produced by the mic, preamp, interface etc. I've made a test recording. I just don' know which of Cooledit's figuresis the relevant one

Noise Floor

Reply #3 –
Quote from: botface on
Min Sample Value:   -51
Max Sample Value:   55
Actual Bit Depth:   16 Bits
Peak Amplitude:   -55.42 dB
Possibly Clipped:   0
DC Offset:   -.002


These values are related, and tell about what has been recorded.
Bit depth 16 implies a range of -32768 to 32767.  From the max sample value and the range, one gets the peak dB -> 20 * log10(55/32768) = -55.50dBFS (I am not sure why this differs slightly).

The Offset tells about how centered the signal is, Min and max value are not centered. What I am unsure is what the -.002 means. (it's not the difference value versus peak)


Quote from: botface on
Minimum RMS Power:   -80.12 dB
Maximum RMS Power:   -71.2 dB
Average RMS Power:   -77.74 dB
Total RMS Power:   -77.59 dB

Using RMS Window of 50 ms


This gives information about the power of the signal. It is an analysis over time (the window). The total is , i guess, when the window is the whole signal.

So, since you calibrated the signal to have peaks around -6dBFS when playing, and the analysis says that the "silence" (noise ground) peaks are at -55.5dBFS, you have around 50dB of SNR for the recordings you intend to do.

What could matter is what type of noise floor you have, if it is white, or has some frequency content (either low frequency from power line, fluorescent lights, etc..) . That could be something to improve.

Noise Floor

Reply #4 –
Quote from: botface on
Quote from: Arnold B. Krueger on
Quote from: botface on
I'm trying to ascertain the noise floor of my recording space. I set up my levels to what I would normally use to record acoustic guitar so it that peaks at around -6dbfs. Then I recorded "silence". Cooledit gives the figures below from its Statistical Info tool. So what's my noise floor - the Peak Amplitude figure, the Average RMS Power figure, something else?

   Mono
Min Sample Value:   -51
Max Sample Value:   55
Peak Amplitude:   -55.42 dB
Possibly Clipped:   0
DC Offset:   -.002
Minimum RMS Power:   -80.12 dB
Maximum RMS Power:   -71.2 dB
Average RMS Power:   -77.74 dB
Total RMS Power:   -77.59 dB
Actual Bit Depth:   16 Bits

Using RMS Window of 50 ms


In order to measure SPL you need some kind of acoustically calibrated device, or an acoustical calibrator to calibrate the mic, preamp, and analytical software that you have.

Measurements of noise only make sense when they are taken over a defined bandwidth.

Sorry, badly worded question. I'm not trying to measure the ambient noise level of the room, I'm trying to get a feel for the noise content relative to a healthy signal of a typical recording made in that room. So, it would include noise produced by the mic, preamp, interface etc. I've made a test recording. I just don' know which of Cooledit's figuresis the relevant one


The part about noise measurements only being valid over a defined bandwidth still applies.

I'd put an A and or C weighting filter into CoolEdit as a drawn-in FFT filter  from one of the many online references, and then use one of the CE  RMS statistics numbers. IOW Analyze, Statistics, Average RMS,.