Eventide Punctuate

Science Behind Punctuate

Humans can only detect the presence of a tone if it is a certain distance from another tone playing at the same time. The Mel Scale defines the arrangement of auditory frequency bands such that each band sounds equally spaced from all others. This division of sound describes how humans hear. Most graphic EQs are IIR (infinite impulse response) or analog-style filters. These have a lot of great properties, but unfortunately, the shape of an IIR filter isn’t very flexible. For instance, even with every band set flat, the total filter shape isn’t actually flat. Furthermore, when you boost or cut each band you’re affecting the ones next to it as well. Punctuate uses a linear phase FIR (finite impulse response) filter that doesn’t have these problems so what you hear is true to what you see on the screen.

Instead of using what DSP engineers call “ideal” rectangular FIR filters, these are triangularly shaped filters. These are often used in hearing models as a first approximation to the critical bands in your inner ear. When you shape filters like the ones in your ear, the filtered signal sounds natural. In a complex signal, at any given time, you can really only hear one sound source in each filter.

Punctuate uses these filters to break the incoming audio signal into the 26 critical bands, and runs a transient shaper on each band for unprecedented control over the transients of the audio signal. By doing this, Punctuate allows you to add punch in only the places where the signal needs, instead of just slamming the level of the entire signal up and down at the transient point. Because you have independent control over the bands, you can even emphasize transients in some bands while suppressing them in others. And because it’s based on Critical Bands, it does this in such a way that sounds natural to the human ear, so you don’t hear any artifacts. Finally, Punctuate allows you to smooth the transient modulation across bands using the ADAPTIVE TRANSIENT control. This allows you to run the bands independently for ultimate control, or couple them for a smoother sound.