# vDSP.Biquad A single- or double-precision biquadratic filter. ``` struct Biquad where T : vDSP_FloatingPointBiquadFilterable ``` ## Overview> Note: > The vDSP biquadratic filters work in place. That is, the source and destination pointers may point to the same memory. ## Topics ### Initializers [`init(coefficients:channelCount:sectionCount:ofType:)`](/documentation/Accelerate/vDSP/Biquad/init(coefficients:channelCount:sectionCount:ofType:)) Creates a new single-channel or multichannel cascaded biquad IIR structure. ### Instance methods [`apply(input:)`](/documentation/Accelerate/vDSP/Biquad/apply(input:)) Applies a single- or double-precision single-channel or multichannel biquad IIR filter, returning the filtered signal. [`apply(input:output:)`](/documentation/Accelerate/vDSP/Biquad/apply(input:output:)) Applies a single- or double-precision single-channel or multichannel biquad IIR filter, overwriting the supplied output vector. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)