Weighting Filter

Weighted frequency response filter

expand all in page

Library:
Audio Toolbox / Filters

Description

The Weighting Filter block performs frequency-weighted filtering independently across each input channel.

Ports

Input

expand all

`Port_1` — Input signal
matrix | 1-D vector

Matrix input –– Each column of the input is treated as an independent channel.
1-D vector input –– The input is treated as a single channel.

Data Types: single | double

Output

expand all

`Port_1` — Output signal
matrix

The Weighting Filter block outputs a signal with the same data type as the input signal. The size of the output depends on the size of the input:

Matrix input –– The block outputs a matrix the same size and data type as the input signal.
1-D vector input –– The block outputs an N-by-1 matrix (column vector), where N is the number of elements in the 1-D vector.

Data Types: single | double

Parameters

expand all

If a parameter is listed as tunable, then you can change its value during simulation.

`Weighting method` — Type of frequency weighting
`A-weighting` (default) | `C-weighting` | `K-weighting`

See A-Weighting, C-Weighting, and K-Weighting for the definition of the weighting curves.

Tunable: No

`Inherit sample rate from input` — Specify source of input sample rate
`off` (default) | `on`

When you select this parameter, the block inherits its sample rate from the input signal. When you clear this parameter, you specify the sample rate in Input sample rate (Hz).

Tunable: No

`Input sample rate (Hz)` — Sample rate of input
`44100` (default) | `positive scalar`

Tunable: Yes

Dependencies

To enable this parameter, clear the Inherit sample rate from input parameter.

`Simulate using` — Specify type of simulation to run
`Code generation` (default) | `Interpreted execution`

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

Tunable: No

`Mask for attenuation limits` — Creates a mask for filter response visualization
`No mask` (default) | `Class 1` | `Class 2`

The mask attenuation limits are defined in the IEC 61672-1:2002 standard.

If the mask is green, the design is compliant.
If the mask is red, the design breaks compliance.

Tunable: Yes

Dependencies

To enable this parameter, set Weighting method to A-weighting or C-weighting.

`Visualize filter response` — Open plot to visualize magnitude response and compliance mask
button

A 2048-point FFT is used to calculate the magnitude response.

Tunable: Yes

Model Examples

Apply Frequency Weighting

Examine the Weighting Filter block in a Simulink® model and tune parameters.

Block Characteristics

Data Types	`double` \| `single`
Direct Feedthrough	`no`
Multidimensional Signals	`no`
Variable-Size Signals	`yes`
Zero-Crossing Detection	`no`

More About

expand all

A-Weighting

The A-curve is a wide bandpass filter centered at 2.5 kHz, with approximately 20 dB attenuation at 100 Hz and 10 dB attenuation at 20 kHz. A-weighted SPL measurements of noise level are increasingly found in sales literature for domestic appliances. In most countries, the use of A-weighting is mandated for the protection of workers against noise-induced deafness. The ISO and ICOA standards mandate A-weighting for all civil aircraft noise measurements.

The ANSI S1.42.2001 [1] defines this weighting curve. The IEC 61672-1:2002 [2] standard defines the minimum and maximum attenuation limits for an A-weighting filter.

ANSI S1.42.2001 defines the weighting curve by specifying analog poles and zeros. Audio Toolbox™ converts the specified poles and zeros to the digital domain using a bilinear transform:

C-Weighting

The C-curve is "flat," but with limited bandwidth: It has –3 dB corners at 31.5 Hz and 8 kHz. C-curves are used in sound level meters for sounds that are louder than sounds intended for A-weighting filters.

The ANSI S1.42-2001 [1] defines the C-weighting curve. The IEC 61672-1:2002 [2] standard defines the minimum and maximum attenuation limits for C-weighting filters.

ANSI S1.42.2001 defines the weighting curve by specifying analog poles and zeros. Audio Toolbox converts the specified poles and zeros to the digital domain using a bilinear transform:

K-Weighting

The K-weighting filter is used for loudness normalization in broadcast. It is composed of two stages of filtering: a first stage shelving filter and a second stage highpass filter.

The ITU-R BS.1770-4 [3] standard defines this curve.

Assume a second-order filter.

The table shows the coefficients for the filters.

First Stage Shelving Coefficients	Second Stage Highpass Coefficients
$a_{1} = - 1.69065929318241$	$a_{1} = - 1.99004745483398$
$a_{2} = 0.73248077421585$	$a_{2} = 0.99007225036621$
$b_{0} = 1.53512485958697$	$b_{0} = 1.0$
$b_{1} = - 2.6916918940638$	$b_{1} = - 2.0$
$b_{2} = 1.19839281085285$	$b_{2} = 1.0$

The coefficients presented by ITU-R BS.1770-4 are defined for 48 kHz. These coefficients are recomputed for nonstandard sample rates using the algorithm described in [4].

References

[1] Acoustical Society of America. Design Response of Weighting Networks for Acoustical Measurements. ANSI S1.42-2001. New York, NY: American National Standards Institute, 2001.

[2] International Electrotechnical Commission. Electroacoustics Sound Level Meters Part 1: Specifications. First Edition. IEC 61672-1. 2002-2005.

[3] International Telecommunication Union. Algorithms to measure audio programme loudness and true-peak audio level. ITU-R BS.1770-4. 2015.

[4] Mansbridge, Stuart, Saoirse Finn, and Joshua D. Reiss. "Implementation and Evaluation of Autonomous Multi-track Fader Control." Paper presented at the 132nd Audio Engineering Society Convention, Budapest, Hungary, 2012.

Documentation

Weighting Filter

Description

Ports

Input

`Port_1` — Input signal
matrix | 1-D vector

Output

`Port_1` — Output signal
matrix

Parameters

`Weighting method` — Type of frequency weighting
`A-weighting` (default) | `C-weighting` | `K-weighting`

`Inherit sample rate from input` — Specify source of input sample rate
`off` (default) | `on`

`Input sample rate (Hz)` — Sample rate of input
`44100` (default) | `positive scalar`

Dependencies

`Simulate using` — Specify type of simulation to run
`Code generation` (default) | `Interpreted execution`

`Mask for attenuation limits` — Creates a mask for filter response visualization
`No mask` (default) | `Class 1` | `Class 2`

Dependencies

`Visualize filter response` — Open plot to visualize magnitude response and compliance mask
button

Model Examples

Apply Frequency Weighting

Block Characteristics

More About

A-Weighting

C-Weighting

K-Weighting

References

Extended Capabilities

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

See Also

Audio Toolbox Documentation

Support

Documentation

Weighting Filter

Description

Ports

Input

Port_1 — Input signal matrix | 1-D vector

Output

Port_1 — Output signal matrix

Parameters

Weighting method — Type of frequency weighting A-weighting (default) | C-weighting | K-weighting

Inherit sample rate from input — Specify source of input sample rate off (default) | on

Input sample rate (Hz) — Sample rate of input 44100 (default) | positive scalar

Dependencies

Simulate using — Specify type of simulation to run Code generation (default) | Interpreted execution

Mask for attenuation limits — Creates a mask for filter response visualization No mask (default) | Class 1 | Class 2

Dependencies

Visualize filter response — Open plot to visualize magnitude response and compliance mask button

Model Examples

Apply Frequency Weighting

Block Characteristics

More About

A-Weighting

C-Weighting

K-Weighting

References

Extended Capabilities

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

See Also

Audio Toolbox Documentation

Support

`Port_1` — Input signal
matrix | 1-D vector

`Port_1` — Output signal
matrix

`Weighting method` — Type of frequency weighting
`A-weighting` (default) | `C-weighting` | `K-weighting`

`Inherit sample rate from input` — Specify source of input sample rate
`off` (default) | `on`

`Input sample rate (Hz)` — Sample rate of input
`44100` (default) | `positive scalar`

`Simulate using` — Specify type of simulation to run
`Code generation` (default) | `Interpreted execution`

`Mask for attenuation limits` — Creates a mask for filter response visualization
`No mask` (default) | `Class 1` | `Class 2`

`Visualize filter response` — Open plot to visualize magnitude response and compliance mask
button

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