96kHz Investigation

Does content above 20kHz produce anything audible?

Check for 96kHz sample rate

96kHz has been set, but sample-rate-conversion may happen if the interface is being shared.

Start testing

Great, you have audio above audio range.

Now test the audibility of some high frequency content audio files.

Test Waves Setup

Test Waves Setup

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Selection of sampled waveform to use as reference.

Reference

Test Wave 1 - Single Tone

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First test wave, adds a single sine wave at the specified frequency. Investigate basics of audibility and intermodulation.

-1 ?
Level and frequency of a sine wave, mixed in to the main sound. Frequency set directly.

Test Wave 2 - Double Tone

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Second test wave, adds two sine waves at the specified frequencies. Investigate more complex intermodulation components.

-1 ?
Level and frequency of a first sine wave, mixed in to the main sound. Frequency set directly.
-1 ?
Level and frequency of a second sine wave, mixed in to the main sound. Frequency set directly.

Test Wave 3 - Noise

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Third test wave, adds noise to the signal above the ultrasonic threshold set below.

off ?

Amount of noise to add.

Colour varies from white (0db) to pink (-3db).

The level at 1Khz is about the same for each.

Uses the main pitch envelope.

Test Wave 4 - Saturation

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Fourth test wave, creates harmonics using Tanh distortion of the signal, added above the ultrasonic threshold set below.

0% ?
Tanh distortion, commonly used in Saturation modelling

High-Pass

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The noise and distortion test waves are synthesised by high-pass filtering the added components and mixing them in with the reference sample.

0% ?
Cut off frequency of the high pass filter (for noise and Saturation)

Preview:

FFT of Input



FFT and Test

Test your interface

Connect the input of your sound interface to the output and monitor the test signal.

You can do this by:

  • Using the software mixer for the interface.
  • Using a cable to connect the output to the input.
  • Using an external mixer or microphone.

FFT of Output

FFT of Input

For a valid test, you should see sound well over 20Khz and ideally up to 40kHz.

MUSHRA-like Testing

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A MUSHRA inspired test, a methodology which is supposed to address some of the issues with ABX testing.

The reference has no processing applied and is a 44.1kHz sample.

Several sounds are using the parameters below, as well as an "anchor" sound that is reduced quality.

Rank each sound according to the criteria of the test.

The graph is for feedback that a sound is playing but noise is deliberately added to obscure the waveforms, so they won't match.

This is only a proof of concept and isn't meant for serious scientific research.

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

https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1534-3-201510-I!!PDF-E.pdf

Test

Score

100

Identical

80

Close

60

Similar

40

Distinct

20

Different

0

Criterion: Similarity to A (no High Frequency content)

MUSHRA-like Testing - Results

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A MUSHRA inspired test, a methodology which is supposed to address some of the issues with ABX testing.

The heat map show's where your scores were, the black dots show the mean score.

The thin blue line is the line of best fit. The wide band shows the expected line.

More analysis metrics are being considered....

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

https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1534-3-201510-I!!PDF-E.pdf

Sound
P-Value*
Meaning

*Probability that "The sound is indistinguishable from reference A" (Null Hypothesis)