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What? Recess is over?
I don't make the rules around here.
What? Recess is over?
Exactly.
True, but luckilly ignore function helps adults to have a normal discussion.
THD in the reverberation field has little meaning.
Just subscribed to Audioxpress, by the way
And that measurement microphone's distortion is part of the unknowns.
I feel they have gone downhill lately, pushing a lot of woo to please their advertisers.
If you could PM me with some examples, I'd be curious to know. When I've criticized woo and the performance of products aimed at the woo crowd and the companies complained, my editor stood by me quite firmly.
I was referring the time it takes for the physical buildup of the resonance mode in the room, and is not related to the "accuracy" of the measurement method.The sweep's rate of frequency change has no bearing on this. What matters is the total duration of the sweep plus the duration of the capture after the sweep ends. Measurement sweeps run low frequency to high, so even very severe low frequency resonances are unlikely to be above the noise floor by the end of the captured content unless measuring a very large space with a very short sweep.
I don't have any recent issues handy, but look at the intro pieces by the editor (recent ones I remember have been pushing MQA and hi-res), the show reports and the vendor profiles.
I hope you think the equipment reviews are fair and balanced.
It doesn't. With a sweep the stimulus is the entire sweep. The response to that stimulus needs to be captured, ideally at least to the point it falls below the measurement system's noise floor. In the limit a sweep spends zero time at any specific frequency, but that is irrelevant to its purpose as a stimulus to derive the system's impulse response, which will be accurately obtained in the absence of gross truncation of the response. The impulse response will faithfully capture the time domain behaviour of the system.I was referring the time it takes for the physical buildup of the resonance mode in the room, and is not related to the "accuracy" of the measurement method.
I borrowed this figure from this webpage as an example. The resonance frequency is 0.398 Hz. However, if you excite it for 25 seconds and measure (~10 periods) vs 50 seconds (~20 periods) , you'll get different amplitudes because in this case it takes ~100 s to reach steady state. This gives a probable cause for the differences in the resonance peak heights measured with a sweep vs measured at a stationary frequency.
I think you are correct. The mathematics is pretty clear on this. ThanksIt doesn't. With a sweep the stimulus is the entire sweep. The response to that stimulus needs to be captured, ideally at least to the point it falls below the measurement system's noise floor. In the limit a sweep spends zero time at any specific frequency, but that is irrelevant to its purpose as a stimulus to derive the system's impulse response, which will be accurately obtained in the absence of gross truncation of the response. The impulse response will faithfully capture the time domain behaviour of the system.
This kind of info is not easily available.For some measurement mics, but generally good ones aren't going to be your limitation. The big issue at any reasonable and meaningful test level and distance is still noise (room, mostly), mic distortion runs a distant third except at really high SPL. That's why I usually use a PCB Piezotronics 376A32 1/2" phantom calibrated omni for 1M and room measurement, but switch to a 376A31 1/4" for Keele-style near-field.
I guess the dashed lines are 2nd and 3rd harmonics ?
Could you add the (averaged) noisefloor level ?
That's an interesting measurement.
How exactly are you doing it?
One sine wave per 1/12th octave?
Then you limit the measurement time to avoid reflections? That's what you mean by "gated"?
If 7ms is the gate time, how do you measure below 140Hz?