MultibandProcessing

Multiband processing is an audio signal processing technique that divides a signal into multiple frequency bands using a filter bank or crossover network and applies independent processing to each band before recombining them. This approach enables targeted control over dynamics, tone, and other characteristics within specific spectral regions, reducing unintended effects on the rest of the signal.

A typical multiband processor comprises three elements: a crossover or filter bank that splits the incoming signal into bands (for example, low, mid, and high frequencies), per-band processing modules (such as compressors, expanders, limiters, and equalizers), and a recombination path that sums the processed bands back into a single output. Phase alignment and crossover design are important, as imperfect band boundaries can cause artifacts or coloration when bands are recombined.

Common applications include dynamic processing, where multiband compression or limiting targets only certain frequency regions to control loudness and transients without altering the entire spectrum. Per-band equalization or tonal shaping is another use, as is noise reduction and spectral editing. Multiband processing is widely employed in mastering to achieve loudness and tonal balance, and in tracking or post-production to manage transient-rich sources like drums or vocals.

Implementation considerations include the number of bands, the type of filters (crossover design and phase behavior), latency, and potential interactions at band boundaries. Digital implementations typically use fixed or adaptive bands with varying degrees of transparency to minimize artifacts. While offering powerful control, multiband processing adds complexity and requires careful calibration to preserve naturalness and avoid audible seams.