hum

Builtin index · Noise

result = hum(x, fs, [freq=50], [harmonics=3], [snr=20], [amplitude=], [seed=])

Input: x, fs, freq, harmonics, snr, amplitude, seed · Output: result

What it is

Adds simulated mains pickup to x, a length-N signal vector, given the sample rate fs in Hz. freq (number, Hz) is the mains fundamental, default 50. harmonics (integer count) is how many odd harmonics to include — 3 means the 1st, 3rd and 5th, i.e. 50, 150 and 250 Hz — default 3. snr (number, dB, default 20) or amplitude (number, raw units) sets the interference level, one or the other, not both. seed (integer, optional) fixes the phase/noise draw for a reproducible run.

Overloads

One call shape — this function is not overloaded.

Examples

From the documentation, and run by the build -- the output and the figure below are what the engine actually produced. Simplest first.

fs = 1000
t = (0 to 999) / fs
clean = sin(2 * pi * 7 * t)

h = hum(clean, fs, freq = 50, harmonics = 3, snr = 6)
e = emf(clean, fs, carrier = 150, snr = 6)
print("hum {measure_snr(clean, h):.2f} dB, emf {measure_snr(clean, e):.2f} dB")

hum 6.00 dB, emf 6.00 dB

from noise

How it works

hum(x, fs, freq = 50, harmonics = 3, snr = 20) — mains pickup, with its ODD harmonics. harmonics = 3 means 50, 150 and 250 Hz: mains arrives through a symmetric nonlinearity, which generates odd harmonics only, and a notch at the fundamental alone leaves the rest behind.

From the note above this builtin in the interpreter, where the reasoning was written down as it was built.