Audio engineering test/sample file resources, and online generators and online audio tests

Some handy audio test file and test generator resources

- AudioCheck - Internet's largest collection of Sound Tests, Audio Test Tones, and Tone Generators. Online and Free!

- AudioCheck: Pink noise test tones. Includes excellent description of pink noise principles. Pink noise sample files generated using wavTones' professional grade Pink Noise Generator. Download Pink Noise CD Quality WAV.

- AudioCheck: High Definition Audio test files, but only it seems "high definition" in the sense of sample rates higher than 44.1kHz. Frequency sweeps, chirp tones, white noise, pink noise. Includes Pink Noise: 96kHz, -3dBFS, 30s, 5.6MB (WAV) BUT ONLY 16-bit.

- AudioCheck: dynamic test tones: A series of pink noise files at full scale then a given number of dB below, down to 72dB and then Mute:

'Nowadays, much emphasis is placed on 24-bit recordings, with a dynamic range exceeding 140dB. Use these test tones to realize how 16-bit supersedes by far the dynamic range offered by your listening environment.

"At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need? (a quote from the internet)." '

I downloaded them and performed tests on them as reported here: [node/3247].

- Ten-minute clips of white noise, pink noise and Brownian noise. Recorded in stereo at a 24-bit 48-kHz rate. Synthesized with Sound Forge Software. Available in 24bit FLAC, Ogg Vorbis, 64Kbps MP3, and VBR MP3.

- Sound tests and clips: WAV 48KHz, 16bit stereo. Examples: LRMonoPhase, piano, some organ sounds. Maybe more useful Pink Noise, 48k/32Float, Stereo, 3.7MB.

- A very useful list of Free 24/96 Downloads.

- Label where you can download sample FLAC and WAV in 24 Bit / 96 kHz & 24 Bit / 192 kHz files

- LINN Records test files: 16-bit and 24-bit ALAC and FLAC, 320kbps MP3 (sample rates not stated).

- Sound Keeper Recordings Format comparison: includes 16-bit/44kHz, 24-bit/96kHz, 24-bit/192kHz zipped WAV files.

- Steinway and Sons: Three excerpts from Franz Liszt's Mephisto Waltz No. 1, in Original: 24 bit / 96 kHz (103 MB) vs. CD quality: 16 bit / 44.1 kHz (32 MB).

- HIRES FLAC testbench downloads: Mozart, Beethoven etc. FLAC 24-bit/192kHz, FLAC 24-bit/96kHz ..

Listening and format comparison tests (for fun and humility)

- Up to the challenge? Do 320kbps mp3 files really sound better? Take the test!

- AudioCheck: Blind Listening Tests. A heap of truly humbling sound tests that some self-proclaimed audiophiles would be too scared to try. Try them with your cheapest headphones possible to thwart the tests completely, or do it properly and use very expensive audiophile speakers and best quality equipment .. and get almost exactly the same result.

Monty Montgomery's high definition and ultrasonic audio test files

This is a super article 24/192 Music Downloads ... and why they make no sense including ultrasonic "intermod" tests:

'a 30kHz and a 33kHz tone in a 24/96 WAV file, a longer version in a FLAC, some tri-tone warbles, and a normal song clip shifted up by 24kHz so that it's entirely in the ultrasonic range from 24kHz to 46kHz ..'Assuming your system is actually capable of full 96kHz playback, the .. files should be completely silent with no audible noises, tones, whistles, clicks, or other sounds. If you hear anything, your system has a nonlinearity causing audible intermodulation of the ultrasonics.'

Well I played the normal song clip shifted up by 24kHz [10 sec WAV] and on my MacBook Pro 17" early 2008 (and listened with quality headphones) I could easily hear lots of audible noises, and even the basic rhythm and some melody of the original song ! Therefore, my MacBook Pro system, although claiming to by capable of 24-bit 96kHz (and setup correctly for it) 'has a nonlinearity causing audible intermodulation of the ultrasonics' !

I also heard lots, easily, on these ultrasonic warble files:

26kHz - 48kHz warbling tones (24 bit / 96kHz) [10 second WAV]
26kHz - 96kHz warbling tones (24 bit / 192kHz) [10 second WAV]

Monty also includes some test files that prove that 16-bit can represent arbitrary sounds quieter than the oft quoted -96dB (which is merely an RMS value, not a limit):

'I have linked to two 16 bit audio files here; one contains a 1kHz tone at 0 dB (where 0dB is the loudest possible tone) and the other a 1kHz tone at -105dB.

Sample 1: 1kHz tone at 0 dB (16 bit / 48kHz WAV)

Sample 2: 1kHz tone at -105 dB (16 bit / 48kHz WAV)

Above: Spectral analysis of a -105dB tone encoded as 16 bit / 48kHz PCM. 16 bit PCM is clearly deeper than 96dB, else a -105dB tone could not be represented, nor would it be audible. How is it possible to encode this signal, encode it with no distortion, and encode it well above the noise floor, when its peak amplitude is one third of a bit? Part of this puzzle is solved by proper dither, which renders quantization noise independent of the input signal. ..'

I performed some spectrum analysis in Audacity on some of these Monty test files, visit: Audacity: miscellaneous tips.

On the 16-bit "sound capture below 96kB" proof:

On the 30kHz-33kHz ultrasonic 24-bit 96kHz file: