I’m going to be experimenting with different sound recording arrangements in the next week, and need a qualitative way to compare them.
Mono, I don’t need stereo.

We’re all familiar with video test patterns for video screens, and printer test patterns. Patterns that anyone can use to tell how good the colour resolution and quality is.

Is there anything equivalent in audio?

Something I can play and record to test such things as spectrum flatness, clipping, unwanted reverb, popping sounds, growling, background noise, feedback, hum, sibilance.

For example as an analogue of black and white bars, an increasingly rapid switching of two frequencies to test for an arpeggio being distorted to sound like a chord.

The old cassette tapes used to have a series of beeps of various tones as a sound check before the music started.

this one is fairly typical

https://www.youtube.com/watch?v=dQw4w9WgXcQ

but may not suit all tastes

I have an Audio Test CD that came out in the early 2000s which might be suitable for you.

Is this the sort of material you’re after?

Tracks:

1 Left-Right
2 Left, Right, Center, Surround (like Dolby Pro-Logic)
3 Dual Tone 700 L, 1k R 0dB 30s
4 700 0dB 30s
5 1k 0dB 60s
6 Log Sweep 20 to 20k, 0dB to -6dB, 32s
7 Linear Sweep 20 to 20k, 0dB to -6dB, 32s
8 80Hz warble +-40Hz -1dB 60s
9 100Hz warble +-40Hz -1dB 60s
10 120Hz warble +-40Hz -1dB 60s
11 16 -1dB 30s
12 20 -1dB 30s
13 25 -1dB 30s
14 31.5 -1dB 30s
15 40 -1dB 30s
16 50 -1dB 30s
17 60 -1dB 30s
18 63 -1dB 30s
19 70 -1dB 30s
20 80 -1dB 30s
21 90 -1dB 30s
22 100 -1dB 30s
23 125 -1dB 30s
24 160 -1dB 30s
25 200 -1dB 30s
26 250 -1dB 30s
27 315 -1dB 30s
28 400 -1dB 30s
29 500 -1dB 30s
30 630 -1dB 30s
31 800 -1dB 30s
32 1250 -1dB 30s
33 1600 -1dB 30s
34 2k -1dB 30s
35 2500 -1dB 30s
36 3150 -1dB 30s
37 4k -1dB 30s
38 5k -1dB 30s
39 6300 -1dB 30s
40 8k -1dB 30s
41 10k -1dB 30s
42 12500 -1dB 30s
43 16k -1dB 30s
44 20k -1dB 30s
45 Piano A4 440Hz
46 Piano solo, stereo
47 Drum solo, stereo
48 Digital Metronome 120bpm 4mins
49 Crest Wave 10s
50 DC Offset 10% Inverted Polarity 20s
51 DC Offset Full!! Inverted Polarity 20s
52 1k Inverted Polarity 0dB 30s
53 1k -60dB 10s
54 1k Square -2dB 30s
55 1k Square 0dB!! 30s
56 White Noise -9dB 60s
57 440 -1dB 20mins
58 Pink Noise -12dB 20mins
59 Digital Silence 2mins

AussieDJ said:

I have an Audio Test CD that came out in the early 2000s which might be suitable for you.

Is this the sort of material you’re after?

Tracks:

1 Left-Right
2 Left, Right, Center, Surround (like Dolby Pro-Logic)
3 Dual Tone 700 L, 1k R 0dB 30s
4 700 0dB 30s
5 1k 0dB 60s
6 Log Sweep 20 to 20k, 0dB to -6dB, 32s
7 Linear Sweep 20 to 20k, 0dB to -6dB, 32s
8 80Hz warble +-40Hz -1dB 60s
9 100Hz warble +-40Hz -1dB 60s
10 120Hz warble +-40Hz -1dB 60s
11 16 -1dB 30s
12 20 -1dB 30s
13 25 -1dB 30s
14 31.5 -1dB 30s
15 40 -1dB 30s
16 50 -1dB 30s
17 60 -1dB 30s
18 63 -1dB 30s
19 70 -1dB 30s
20 80 -1dB 30s
21 90 -1dB 30s
22 100 -1dB 30s
23 125 -1dB 30s
24 160 -1dB 30s
25 200 -1dB 30s
26 250 -1dB 30s
27 315 -1dB 30s
28 400 -1dB 30s
29 500 -1dB 30s
30 630 -1dB 30s
31 800 -1dB 30s
32 1250 -1dB 30s
33 1600 -1dB 30s
34 2k -1dB 30s
35 2500 -1dB 30s
36 3150 -1dB 30s
37 4k -1dB 30s
38 5k -1dB 30s
39 6300 -1dB 30s
40 8k -1dB 30s
41 10k -1dB 30s
42 12500 -1dB 30s
43 16k -1dB 30s
44 20k -1dB 30s
45 Piano A4 440Hz
46 Piano solo, stereo
47 Drum solo, stereo
48 Digital Metronome 120bpm 4mins
49 Crest Wave 10s
50 DC Offset 10% Inverted Polarity 20s
51 DC Offset Full!! Inverted Polarity 20s
52 1k Inverted Polarity 0dB 30s
53 1k -60dB 10s
54 1k Square -2dB 30s
55 1k Square 0dB!! 30s
56 White Noise -9dB 60s
57 440 -1dB 20mins
58 Pink Noise -12dB 20mins
59 Digital Silence 2mins

Wow yes! How do I get something like that?

mollwollfumble said:

AussieDJ said:

I have an Audio Test CD that came out in the early 2000s which might be suitable for you.

Is this the sort of material you’re after?

Tracks:

1 Left-Right
2 Left, Right, Center, Surround (like Dolby Pro-Logic)
3 Dual Tone 700 L, 1k R 0dB 30s
4 700 0dB 30s
…

Wow yes! How do I get something like that?

Looking for similar on the web.
So far found similar, but not as good.

eg. AussieDJ list is the only one I’ve seen with a square wave.
A square wave is a very sensitive test for resonance. A pure tone is not.

Moll, how do we get in touch?

Obviously wary of putting personal or other details on an open forum.

AussieDJ said:

Moll, how do we get in touch?

Obviously wary of putting personal or other details on an open forum.

I don’t mind handing out my email.
david_paterson
at
netspace.net.au

Many years ago I did post my house address on the forum, in a subtle way, but that link is now well and truly buried.

Thank you!

Email coming soon.

Got it.

Brilliant. All I’ll ever want. I’ve already found that my mono speaker is missing the right channel. Not a problem with mono recording, but may give strange results when playing classical from ewetube. I may be able to fix that.

I like the warnings in the “using the tracks” file. Particularly on tracks 54-55: “Watch out for these tracks! Turn your amps off first! These are sometimes used in destructive testing at audio R&D labs… Don’t run them at high volumes if at all. The most vulnerable part of your system are the HF drivers which can fry”. I was intending to use that track for testing for excess reverb, but now I think not.

I’ve never used an equaliser seriously. I move the microphone around relative to the piano to emphasise high or low tones, usually high because in mrs m’s playing the harmony is so rich that the melody can get lost in it. Now with AussieDJ’s CD I can actually use the equaliser seriously the way it’s meant to be used.

My first step will be opening up a set of tracks on audacity, then playing them on some other player while recording to audacity. Then detailed comparison of the played and recorded tracks.

I’ve had various problems with my recording system, primarily: digital drop-outs between amp and computer, massive distortion sometimes (I call it growling, I don’t know what the technical term is), clipping, spikes, noise when it’s supposed to be silent, massive loss of volume, dropping the pre-amp on the floor.

mollwollfumble said:

Got it.

Brilliant. All I’ll ever want. I’ve already found that my mono speaker is missing the right channel. Not a problem with mono recording, but may give strange results when playing classical from ewetube. I may be able to fix that.

I like the warnings in the “using the tracks” file. Particularly on tracks 54-55: “Watch out for these tracks! Turn your amps off first! These are sometimes used in destructive testing at audio R&D labs… Don’t run them at high volumes if at all. The most vulnerable part of your system are the HF drivers which can fry”. I was intending to use that track for testing for excess reverb, but now I think not.

I’ve never used an equaliser seriously. I move the microphone around relative to the piano to emphasise high or low tones, usually high because in mrs m’s playing the harmony is so rich that the melody can get lost in it. Now with AussieDJ’s CD I can actually use the equaliser seriously the way it’s meant to be used.

My first step will be opening up a set of tracks on audacity, then playing them on some other player while recording to audacity. Then detailed comparison of the played and recorded tracks.

I’ve had various problems with my recording system, primarily: digital drop-outs between amp and computer, massive distortion sometimes (I call it growling, I don’t know what the technical term is), clipping, spikes, noise when it’s supposed to be silent, massive loss of volume, dropping the pre-amp on the floor.

Do you use Bluetooth between your system and the PC, if so do you find it unreliable ?
I gave up and use it wired including headphones

Cymek said:

Do you use Bluetooth between your system and the PC, if so do you find it unreliable ?
I gave up and use it wired including headphones

Good question. No, it’s wired. That does mean a bit of plug wobble every time one plug slots into another plug, which can come loose. But I feel safer that way.

The following is from Track 6 of AussieDJ’s CD. It’s a log sweep of frequency, and the amplitude on the chart is the amplitude of the music.
The top chart is as played.
The bottom chart is as recorded via .wav playing software, speaker and microphone.

The bottom chart is supposed to be identical to the top one
Ya. Not nearly as smooth a frequency response as I expected. More like a dog’s breakfast.
Not something that would be easy to fix with an equaliser.

I suspect the speaker, rather than the software or microphone. And it’s supposed to be a good speaker, too. One like this.

mollwollfumble said:

Cymek said:

Do you use Bluetooth between your system and the PC, if so do you find it unreliable ?
I gave up and use it wired including headphones

Good question. No, it’s wired. That does mean a bit of plug wobble every time one plug slots into another plug, which can come loose. But I feel safer that way.

The following is from Track 6 of AussieDJ’s CD. It’s a log sweep of frequency, and the amplitude on the chart is the amplitude of the music.
The top chart is as played.
The bottom chart is as recorded via .wav playing software, speaker and microphone.

The bottom chart is supposed to be identical to the top one
Ya. Not nearly as smooth a frequency response as I expected. More like a dog’s breakfast.
Not something that would be easy to fix with an equaliser.

I suspect the speaker, rather than the software or microphone. And it’s supposed to be a good speaker, too. One like this.

I think it’s the microphone. Or, maybe, a combination of microphone and speaker.

This is what Track 6 on that CD looks like (also from Audacity):

What does yours look like?

(In Audacity: Select All (CTRL+A), then Analyze, then plot spectrum)

Coincidentally, this article discusses the frequency response of the SM57:

https://www.behindthemixer.com/importance-microphone-frequency-response/

>The bottom chart is supposed to be identical to the top one

not sure where you’ve got the microphone, or the room dimension, but guessing there’s probably good chance something about the room dimensions are in the sweep you did

transition said:

>The bottom chart is supposed to be identical to the top one

not sure where you’ve got the microphone, or the room dimension, but guessing there’s probably good chance something about the room dimensions are in the sweep you did

Good thought, too.

AussieDJ said:

transition said:

>The bottom chart is supposed to be identical to the top one

not sure where you’ve got the microphone, or the room dimension, but guessing there’s probably good chance something about the room dimensions are in the sweep you did

Good thought, too.

that and furnishings etc

transition said:

AussieDJ said:

transition said:

>The bottom chart is supposed to be identical to the top one

not sure where you’ve got the microphone, or the room dimension, but guessing there’s probably good chance something about the room dimensions are in the sweep you did

Good thought, too.

that and furnishings etc

hope no feedback also, other than the obvious required one for comparison, meaning the recorded input signal needs be isolated from the test signal

transition said:

AussieDJ said:

transition said:

>The bottom chart is supposed to be identical to the top one

not sure where you’ve got the microphone, or the room dimension, but guessing there’s probably good chance something about the room dimensions are in the sweep you did

Good thought, too.

that and furnishings etc

Furnishings are designed to absorb as much sound as possible. But room acoustics could have an effect. I’m pleaser to announce not too much reverb.
Come to think of it, from room shape i ought to be able to calculate peaks and troughs. Or move the speaker and microphone a bit and see how much the recorded sound changes.

Yes, AussieDJ, my track 6 is the same as yours before going to the speakers. :-)
I thought the broad double humps in the recorded version was because the speaker has a woofer and tweeter, one hump for each.

I tried recording both a chromatic scale and a glissando from the piano and get the same broad double humps in the recording volume, so it’s not in the speaker. In addition, the amplification of specific frequencies from the piano is repeatable. I play a chromatic twice and the pattern of amplification is the same.

Additionally, I can hear the broad separation of bass and treble humps straight from the piano, without ANY sound recording or playback equipment involved.
So I really don’t know. Room acoustics could be having a big effect – or – the piano is set up to amplify roughly thr same frequencies as the woofer-tweeter of a speaker.

https://en.wikipedia.org/wiki/Room_modes

mollwollfumble said:

Yes, AussieDJ, my track 6 is the same as yours before going to the speakers. :-)

Just out of curiosity, what does your recovered audio (bottom chart ‘Audio Track #2’) look like if you run a frequency analysis on it?