brusformning

Brusformning, also known as noise shaping, is a signal processing technique used to alter the spectral distribution of quantization noise. By incorporating a feedback or feedforward loop that depends on the quantization error, the method reshapes how quantization noise appears across the frequency spectrum, typically pushing more of the noise outside the signal band.

In practice, brusformning is a key element of oversampled systems such as sigma-delta converters. A quantizer introduces error, which is then fed back through a loop filter. The resulting noise transfer function determines how the quantization noise is distributed: less noise within the band of interest and more at higher frequencies. This enables higher in-band signal quality without raising the sampling rate.

Applications are common in audio DACs and ADCs, where perceptual listening tests favor lower in-band noise. Brusformning is also used in measurement instrumentation and digital communications, often in combination with oversampling and dithering to minimize tonal artifacts.

Design considerations include the order and characteristics of the loop filter, the chosen oversampling ratio, and stability. Higher-order shaping can achieve greater in-band attenuation but may risk instability or ringing if not carefully designed. Dithering may be added to reduce low-level distortion or periodic artifacts, and multi-bit quantizers or different modulator topologies can be employed to balance performance, power, and complexity.

See also: quantization, sigma-delta modulation, oversampling, noise transfer function, dithering.