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Audio Delta

Compute delta features

  • Library:
  • Audio Toolbox / Features

  • Audio Delta block


The Audio Delta block computes the delta of the input audio features. The delta is an approximation of the first derivative of the audio features with respect to time.



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Audio features, specified as a scalar, vector, matrix, or 3-D array. The delta computation operates along the first dimension. All other dimensions are treated as independent channels.

Data Types: single | double


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Delta of audio features, returned as an array that is the same size and data type as the input.

Data Types: single | double


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Window length over which to calculate delta, specified as an odd integer greater than 2.

  • Interpreted execution –– Simulate model using the MATLAB® interpreter. This option shortens startup time but has a slower simulation speed than Code generation. In this mode, you can debug the source code of the block.

  • Code generation –– Simulate model using generated C code. The first time you run a simulation, Simulink® generates C code for the block. The C code is reused for subsequent simulations, as long as the model does not change. This option requires additional startup time, but the speed of the subsequent simulations is comparable to Interpreted execution.

Block Characteristics

Data Types

double | single

Direct Feedthrough


Multidimensional Signals


Variable-Size Signals


Zero-Crossing Detection



The delta of an audio feature x is a least-squares approximation of the local slope of a region centered on sample x(k), which includes M samples before the current sample and M samples after the current sample.


The delta window length defines the length of the region from M to M.

For more information, see [1].


[1] Rabiner, Lawrence R., and Ronald W. Schafer. Theory and Applications of Digital Speech Processing. Upper Saddle River, NJ: Pearson, 2010.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2022b