# Audio electronics measurements and time domain

#### CleanSound

##### Major Contributor
Forum Donor
I have a question, my academic background from over 20 years ago is in digital EE, and the time domain is obviously very relevant in digital circuitry (i.e. clock speed), so I have a question for the analog EE experts out there.

When it comes to electronic audio measurements, we say we are able to measure everything when it comes to audio electronics. However, I have never seen an AP (or any other audio analyzer) measurement where time domain is part of the measurement, for example something like raise time and fall time of an audio signal.

Sure most audio electronics frequency response is flat and a multi-tone test demonstrates the behavior of multiple concurrent frequency. But none of that measurement have the time domain. So the question is, is time domain relevant in analog electronics measurements? If not, why?

#### SIY

##### Grand Contributor
Technical Expert
I have a question, my academic background from over 20 years ago is in digital EE, and the time domain is obviously very relevant in digital circuitry (i.e. clock speed), so I have a question for the analog EE experts out there.

When it comes to electronic audio measurements, we say we are able to measure everything when it comes to audio electronics. However, I have never seen an AP (or any other audio analyzer) measurement where time domain is part of the measurement, for example something like raise time and fall time of an audio signal.

Sure most audio electronics frequency response is flat and a multi-tone test demonstrates the behavior of multiple concurrent frequency. But none of that measurement have the time domain. So the question is, is time domain relevant in analog electronics measurements? If not, why?
There certainly is time domain measurement- that's what gets Fourier transformed.

Frequency and time representations are exactly equivalent.

OP

#### CleanSound

##### Major Contributor
Forum Donor
There certainly is time domain measurement- that's what gets Fourier transformed.

Frequency and time representations are exactly equivalent.
You are certainly correct. Perhaps let me ask the question differently, null testing, which is very dependent on the time domain. Signal raise time and fall time, not just amplitude. Is that something of significance?

#### Blumlein 88

##### Grand Contributor
Forum Donor
You can get some good software if you'd like to try it out yourself. Null testing software.

#### SIY

##### Grand Contributor
Technical Expert
You are certainly correct. Perhaps let me ask the question differently, null testing, which is very dependent on the time domain. Signal raise time and fall time, not just amplitude. Is that something of significance?
Signal rise and fall time are absolutely equivalent to bandwidth- it's all there in either domain, time or frequency- this a key thing to understand in measurement.

OP

#### CleanSound

##### Major Contributor
Forum Donor
Signal rise and fall time are absolutely equivalent to bandwidth- it's all there in either domain, time or frequency- this a key thing to understand in measurement.
And that one simple statement sent me into thinking for a good minute and it just made all the sense to me.

Frequency is measured in cycles per sec., that is the time domain. 1kHz will always have the same raise and fall time, otherwise you can't get 1000 cycles in that 1 sec. So long the equipment/hardware/parts is capable of a specific frequency, by definition raise time and fall time is defined and set for that specific frequency.

EDIT: Can you talk about the validity of null testing?

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#### SIY

##### Grand Contributor
Technical Expert
Frequency is measured in cycles per sec., that is the time domain. 1kHz will always have the same raise and fall time, otherwise you can't get 1000 cycles in that 1 sec. So long the equipment/hardware/parts is capable of a specific frequency, by definition raise time and fall time is defined and set for that specific frequency.
You have grasped the essence of the Fourier theorem, something not everyone can do.

Null testing can be a very informative tool when used properly. DeltaWave is GREAT software.

OP

#### CleanSound

##### Major Contributor
Forum Donor
You have grasped the essence of the Fourier theorem, something not everyone can do.

Null testing can be a very informative tool when used properly. DeltaWave is GREAT software.
I'm sure I was introduced to the Fourier theorem over 20 years ago, whether I get it or not is a different story . I personally find that anything I learn, doesn't always make sense until I think about it years later in more practical sense rather than just the equations.

More on the null test, what information can I get from it and what is it used for?

#### staticV3

##### Master Contributor
More on the null test, what information can I get from it and what is it used for?
Null tests are handy whenever you have organic test signals that don't produce visually intuitive FFT graphs,
and/or signals that aren't compatible with simple algorithms like those that calculate numerical values like THD, SNR, IMD, etc.

To see what information you can get from Null tests, give Deltawave a shot sometime.
There's basic stuff like frequency response and phase, as well as more advanced data like df metric.

#### gnarly

##### Major Contributor
It's easier than null tests, and Deltawave, or whatever test... certainly/pragmatically for the audio bandwidth.

Like SIY says, it's simply linear bandwidth, both frequency magnitude and phase.
Everything else is an overly complicated wtf, imo.

#### Killingbeans

##### Major Contributor
So the question is, is time domain relevant in analog electronics measurements? If not, why?

Because the information is a lot easier to analyze in the frequency domain.

I saw someone mention that the time domain can be useful in acoustics, when you're in a hurry. Fire a blank round or pop a balloon in a room and record it, and it will be close enough to an ideal impulse to let you derive its frequency response with pretty good accuracy.

#### MCH

##### Major Contributor
I saw someone mention that the time domain can be useful in acoustics, when you're in a hurry. Fire a blank round or pop a balloon in a room and record it, and it will be close enough to an ideal impulse to let you derive its frequency response with pretty good accuracy.
(not audio related) in NMR for instance you also get advantage of this: You measure 100s or 1000s of rf pulses to average and increase the SNR

#### ZolaIII

##### Major Contributor
Well you have to most where is relevant the impulse response and square wave in some cases while there is a waterfall plot for speakers in one or another form.
What you won't find is RT60 decay times or ISO 3382-1 tho those are space related not quasi anesthetic chamber. Anyway methodology is evolving and you do have to pay certification and more for each set of standards in order to be able to use them. And equipment in some cases costs the small fortune and if upgrades in precision and capabilities and to minor standard upgrades are small it's a no go even if you have all the money you can spend.

#### SIY

##### Grand Contributor
Technical Expert
(not audio related) in NMR for instance you also get advantage of this: You measure 100s or 1000s of rf pulses to average and increase the SNR
This is the case with most detector noise-limited measurement; you get both throughput and multiplex advantages (Jacquinot and Fellgett) when doing a time domain-FT measurement as opposed to a monochromatic sweep.

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