# Loudness Meter

Standard-compliant loudness measurements

• Library:
• Audio Toolbox / Measurements

## Description

The Loudness Meter block measures the loudness and true-peak of an audio signal based on EBU R 128 and ITU-R BS.1770-4 standards.

## Ports

### Input

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• Matrix input –– Each column of the input is treated as an independent channel. If you use the default Channel weights, specify the input channels in order: [Left, Right, Center, Left surround, Right surround].

• 1-D vector input –– The input is treated as a single channel.

Data Types: `single` | `double`

### Output

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The block outputs a column vector with the same data type and number of rows as the input signal.

Data Types: `single` | `double`

The block outputs a column vector with the same data type and number of rows as the input signal.

Data Types: `single` | `double`

The block outputs a real scalar with the same data type as the input signal.

#### Dependencies

To enable this port, select the Output true-peak value parameter.

Data Types: `single` | `double`

## Parameters

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

The number of elements of the row vector must be equal to or greater than the number of input channels. Excess values in the vector are ignored.

The default channel weights follow the ITU-R BS.1170-4 standard. To use the default channel weights, specify the input to the Loudness Meter block as a matrix whose columns correspond to channels in this order: [Left, Right, Center, Left surround, Right surround].

It is a best practice to specify the channel weights in order: [Left, Right, Center, Left surround, Right surround].

Tunable: Yes

• On — The loudness measurements are relative to the value specified by Target loudness level (LUFS). The output of the block is returned in loudness units (LU).

• Off — The loudness measurements are absolute, and returned in loudness units full scale (LUFS).

Tunable: No

For example, if the Target loudness level (LUFS) is –23, then a loudness value of –24 LUFS is reported as –1 LU.

Tunable: Yes

#### Dependencies

To enable this parameter, select the Use relative scale for loudness measurements parameter.

When you select this parameter, an additional output port, TP, is added to the block. The TP port outputs the true-peak value of the input frame.

Tunable: No

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

Tunable: Yes

#### Dependencies

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

• `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```.

• `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.

Tunable: No

## Block Characteristics

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

## Algorithms

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The Loudness Meter block calculates the momentary loudness, short-term loudness, and true-peak value of an audio signal. You can specify any number of channels and nondefault channel weights used for loudness measurements. The block algorithm is described for the general case of n channels and default channel weights.

## References

[1] International Telecommunication Union; Radiocommunication Sector. Algorithms to Measure Audio Programme Loudness and True-Peak Audio Level. ITU-R BS.1770-4. 2015.

[2] European Broadcasting Union. Loudness Normalisation and Permitted Maximum Level of Audio Signals. EBU R 128. 2014.

[3] European Broadcasting Union. Loudness Metering: 'EBU Mode' Metering to Supplement EBU R 128 Loudness Normalization. EBU R 128 Tech 3341. 2014.