filter

Remove signal — does filtering stop operating? Yes. A filter's entire operation is to select, reject, or reshape signal content. Without the concept of a signal, a filter has nothing to filter, no referent to operate on, and no purpose. The removal test passes: filter needs signal to function.

A filter is defined by its frequency response (passband, stopband, cutoff). Remove frequency-response and the filter's defining characterization mechanism ceases to operate — filters are designed, specified, and understood through their frequency response.

A filter (signal processing filter) is a specific signal processing operation that modifies the frequency content of a signal. A competent speaker calls filtering a type of signal processing technique. Per Law 9: specific→general INSTANCE_OF, nearest kind is signal-processing.

An anti-aliasing filter is a specific kind of filter designed to attenuate frequencies above the Nyquist limit before sampling. A competent speaker would call an anti-aliasing filter 'a filter' — it filters unwanted high-frequency content. Direction: specific (anti-aliasing-filter) → general (filter), per Law 9.

The mel filterbank is a specific kind of filter (a bank of triangular bandpass filters spaced on the mel perceptual scale) used in signal processing. A competent speaker would describe it as 'a filter'. Direction is specific→general (Law 9). Filter is the nearest accepted kind.

A band-pass-filter IS a specific kind of filter: it passes frequencies within a defined band (f_L to f_H) and attenuates everything else. A competent speaker would call it 'a filter'. Nearest kind per Law 11e.

Which existed first? The general concept of a filter (any device or algorithm that selectively passes or attenuates signal components) predates the band-pass variant. The band-pass-filter is a specific instantiation where the pass region is bounded on both sides. The general concept fed into the specific one.

Remove the concept of a filter — does a filter-bank stop OPERATING? Yes. A filter-bank is a structure of parallel filters; its entire function is to apply multiple filters simultaneously. Without the concept of a filter, the filter-bank has no operation. The filter-bank needs filters to function now, not just historically.

Zero-phase-filtering is a specific type of filter — one that introduces zero phase distortion via forward-backward processing. The nearest general kind is 'filter.' Direction: specific→general.

Noise cancellation operates by applying a filter (adaptive, anti-phase, or feedforward) that subtracts or cancels the noise component. Remove the concept of filter and noise cancellation ceases to operate — there is no mechanism left to remove noise. The removal test passes cleanly.

Pre-emphasis applies a first-order filter H(z)=1-μz⁻¹ to boost high frequencies. A competent speaker would call pre-emphasis a type of filter — it is a specific kind of signal filter used for spectral balancing.

The accepted definition carves equalization as an operation that APPLIES a filter with a parameterized gain curve (bandwidth/Q, gain per band, filter topology). Remove the filter mechanism and the operation has no means of adjusting the response — it stops operating. EQ is an operation that applies a filter, not a kind of filter, so DEPENDS_ON is the correct arrow (the rejected zero-phase-filtering case was identity, not mechanism).

Homomorphic filtering is a specific filtering technique that applies filtering operations in a transformed (log) domain to separate multiplicative components. It is a specific kind of filter, not a separate category. A competent speaker would call it a filter.

A crossover is a specific kind of filter: it selectively passes designated frequency bands (routed to a driver) while attenuating the rest, per a designed transfer function — precisely a filter's function, specialized to band-splitting. 'filter' is the nearest available kind (no band-splitter/multiway-filter entry exists), so this is not a leapy INSTANCE_OF. specific->general (Law 9/11e).

A mel-filterbank is a bank of overlapping bandpass filters spaced on the mel scale. Remove filters as an operation and the mel-filterbank has no mechanism — it IS a collection of filter operations. The removal test passes: without filters, a mel-filterbank cannot function.

Equalizer splits an audio signal into multiple frequency bands and independently adjusts the gain of each band — this IS the operation of filtering. Remove the filter mechanism and equalizer has no means of adjusting spectral content. The removal test passes: equalizer needs filters to operate now, not just historically. Direction: equalizer (dependent) → filter (dependency).

Wah-wah sweeps the center frequency of a bandpass filter to produce a vocal-like 'wah' sound. Remove the concept of a filter and wah-wah has no working mechanism — its entire operation IS a time-varying bandpass filter. The removal test passes: wah-wah needs filter to operate now. Direction: wah-wah (dependent) → filter (dependency).

A wah pedal operates by routing audio through a band-pass filter whose center frequency is controlled by a foot pedal. Remove filter and the wah pedal has no mechanism — it IS a filter with a specific control interface. The which-came-first test passes: filter (epoch 0.17) predates wah-pedal (epoch 0.26).

INSTANCE_OF: an equalizer is a specific kind of filter — it is a multi-band frequency-selective device that attenuates or amplifies specific frequency ranges. A competent speaker would call an equalizer 'a filter' (specifically, a set of interconnected filters).

A crossover splits a signal into frequency bands BY MEANS OF frequency-selective filters (a low-pass/high-pass pair, or a bank of band-pass sections). Pinned sense of 'filter': a signal-processing construct that selectively passes or attenuates frequency components based on a designed transfer function. Removal test (Laws 2b/8b): remove the filter — the mechanism object that performs the frequency-selective attenuation — and the crossover has no means of dividing the signal into bands; it stops operating. Not identity (a crossover is a multi-way band-splitting network, not a single filter) and not purpose. Mechanism-object dependency, same family as the accepted limiting→threshold and screwdriver→screw. This is the coherent arrow that replaces the struck crossover→fourier-transform (ambient mathematics, not operation).

A harmonic exciter isolates high frequencies using a bandpass or highpass filter before generating harmonics. Remove the filter and the device would generate harmonics across the entire spectrum, losing its defining behavior of selectively enriching high-frequency content. The removal test passes: no filter = no frequency-selective harmonic generation.

Homomorphic filtering applies filter operations in a transformed domain — it uses linear filters after applying logarithmic compression to the signal. Remove filters and homomorphic filtering has no operational mechanism. The removal test passes: without filters, homomorphic filtering cannot operate.

Specific to general (Law 9): the Wiener filter is a filter in the target's pinned sense — its accepted definition's frequency-domain solution H(f) = S_x(f)/(S_x(f)+S_n(f)) is exactly a designed transfer function that selectively passes or attenuates frequency components (weighted by local SNR), matching the accepted def of 'filter' (selective pass/attenuation per designed transfer function). Nearest kind (Law 11e): no 'optimal-filter' or 'adaptive-filter' rung exists, and iir-filter is the wrong rung — the Wiener filter is defined by the MMSE criterion, not recursion; finite-length Wiener solutions are FIR. Servant-of relations (SERVES speech-enhancement) are a separate matter; this pins the kind-membership sense.

iir-filter (infinite impulse response filter) is a specific type of digital filter that uses feedback. A competent speaker would call it 'a filter'. Nearest kind: filter. IIR filters have feedback coefficients in addition to feedforward.

A phaser works by splitting the signal, passing one path through a cascade of all-pass filters (which are frequency-dependent phase-shift filters), and mixing it back with the dry signal. The interference between the phase-shifted and dry paths creates the characteristic swept notches. Remove filters and the phaser's mechanism vanishes — it cannot operate. Passes Law 8 removal test.

Filter design is the process of creating filter specifications and coefficients. Remove filters and filter design has no operational subject — the entire process is about producing filters. The removal test passes: without filters, filter design ceases to operate.

minimum-phase-filter is a specific kind of filter defined by its phase property.

A comb-filter IS a specific kind of filter: it selectively passes or attenuates frequency components via a designed transfer function whose magnitude response is periodic in frequency (equally spaced peaks and nulls, comb-shaped), realized by delay-and-add. The accepted filter definition — 'selectively passes or attenuates frequency components based on a designed transfer function' — is exactly the genus, and the comb's periodic transfer function is the species. Nearest kind: the map has fir-filter, iir-filter, and all-pass-filter as specific rungs, but a basic comb (y[n]=x[n]+g·x[n-D]) is FIR while a feedback comb is IIR, so neither specific rung covers the construct; 'filter' is the nearest kind that does. Direction: specific→general (Law 9).

fir-filter (finite impulse response filter) is a specific type of digital filter. A competent speaker would call it 'a filter'. Nearest kind: filter (ACCEPTED). Note: fir-filter is a filter that uses only feedforward coefficients.

Frequency-weighting is a specific kind of filter: applies frequency-dependent gain to shape a signal's spectral content. Fits filter's definition as a frequency-dependent modification of a signal.