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Pre-requirements  

Install Octave		 https://octave.org/
	run octave (select software open-cl software render)
	in command window paste:

		pkg install signal -forge
		pkg install data-smoothing -forge

	the file C:\Program Files\GNU Octave\Octave-10.3.0\mingw64\share\octave\site\m\startup\octaverc
		add the line before last few:

			pkg load signal

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96KHz DOWN SAMPLE to 44.1KHz
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Impulse
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A signal with a sample rate of 96 kHz is downsampled to 44.1 kHz. The signal x[n]
consists of 96000 gcd(96000,44100) = 320 unit impulses with enough space between them. The im-
pulses are at sample positions n so that {n mod 320} is a permutation of {0, 1, 2, . . . , 319}.
This basically means that all fractional differences in sample positions between input
and output signal are addressed exactly once. In the later analysis the output signal is
upsampled (by inserting zeros) to lcm(96000, 44100) = 14.112 MHz and the impulse re-
sponses are added to obtain a high resolution impulse response, which is also inspected
in the frequency domain in phase and magnitude utilizing the DF


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Sine Sweep  'sweep-1-48KHz (96KHz Float).wav'
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"A sweep signal with a linear slope of 1 kHz/s from 1 Hz to 44 kHz at a sample rate of
96 kHz is downsampled to 44.1 kHz. Again the spectogram is plotted for analysis to
evaluate aliasing effects and filter cutoff."


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Aliasing Test
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A 23 kHz sine at −4 dBFS for 20 seconds  with a white noise floor of −150 dBFS over 30 seconds is downsampled from 96 kHz to 44.1 kHz. The resulting signal is analysed using Welch’s method with 4 segments, an overlap of 50 %, and a Hann window.


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Intermodulation:
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Again equals the Aliasing test with the difference that the sine is replaced by two sines,
one at 60 Hz, −6 dBFS and the second at 7 kHz, −18.0412 dBFS, which equals quarter
the amplitude of the first sine.