highpass

A biquad high-pass filter. The mirror of lowpass: passes content above cutoff_hz and attenuates content below.

Signature

signal.highpass(cutoff_hz, q) -> Signal

• cutoff_hz — the −3 dB knee.
• q — resonance at the knee. 0.707 for Butterworth (no peak). Higher Q emphasises the cutoff frequency.

Examples

// Cut everything below 100 Hz — kills room rumble or DC offset.
signal.highpass(100.0, 0.707)

// Aggressive "thinned out" tone — keeps just the high content.
signal.highpass(2000.0, 0.707)

// Resonant highpass at 4 kHz — the inverse of a resonant lowpass,
// rare in design but useful for whistle-like character.
signal.highpass(4000.0, 6.0)

When to use it

• Remove low-frequency rumble. Sources from real recordings often carry sub-bass content (room hum, mic handling, DC offset). A high- pass at 60–120 Hz removes it without affecting the audible part.
• Brighten a bass-heavy source. When brown noise or a deep sine is the source, a highpass leaves only the upper edge — useful as a “sizzle” layer in additive synthesis.
• Complement a lowpass. A signal.highpass(800).lowpass(4000) pair makes a wide bandpass with independent Q at each side.

Notes

The same caveats as lowpass: 12 dB/octave roll-off, brief transient response, and use multiple in series for sharper cuts.