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Extract loudness and peak maximum.

The loudness analysis task estimates the perceived loudness of an audio file according to the EBU recommendation R128.
Knowing the loudness of an audio file allows you to adjust one file's overall volume to either a reference level or to the loudness of another file, thus avoiding jumps in the perceived playback level in music players. In most cases, adjusting the LU is trivial: add a gain to your audio file that corresponds to the difference between the extracted and the target LU value. You can also verify the EBU standard compliance of your mixes and productions for your customer or broadcasting station.


Parameter Type Description
access_id required string
One of your personal access_ids.
input_file required file
A file id or file url or a direct file upload (requires POST).

Upload a local file by performing a POST request with encoding-type "multipart/form-data" (corresponding to an html form with an <input type="file" />)

begin_seconds optional float
Skip audio data before this position.
end_seconds optional float
Ignore audio data after this position.
blocking optional bool
[true, false] default: true
Whether to call the task in a blocking or non-blocking way.

Blocking calls return the results directly. For more info see the response documentation for this task.

format optional string
[xml, json, jsonp, xmlp] default: xml
The format to use in the response.

Note that for the formats "jsonp" or "xmlp", the HTTP status code will always be 200.

callback optional string
Callback function name required when using the format "jsonp" or "xmlp."
foo_string optional string
Arbitrary string to add to the logs.

Allows you to add any strings you might find helpful for later analysis of the request logs.



The response gives you a status code, the file_id and the corresponding download URL of the resulting file (audio for process tasks and xml for analyze tasks). For processing reports, use the /file/status request with the parameter format=xml/json/jsonp/xmlp.

Name Description
status The status code of the task.
file_id The unique identifier of the file.
href The direct download link to the file including the file_id


The result provides various measures of loudness and level in the audio file.

Name Type Description
programme_loudness float The loudness of the audio in LU.

The pseudo-unit LU stands for loudness unit. In order to increase or decrease the loudness by one LU, apply a gain of +1 (or -1, respectively) dB to the audio. For your mix to be EBU R128 compliant adjust the loudness to 0 LU (0 LU = -23 LUFS). LU values above 0 LU are possible.

loudness_range float The loudness range (in LU) measures the variation of loudness.

The loudness range is computed from the instantaneous shortterm loudness (see below). High loudness ranges indicate frequent and/or large changes in the programme.

momentary_loudness_max float The overall maximum of the momentary loudness (in LU).

The momentary loudness is a measure with the comparably short integration time of 0.4s.

shortterm_loudness_max float The overall maximum of the shortterm loudness (in LU).

The shortterm loudness is a measure with an integration time of 3s.

truepeak_max float The maximum of the true peak level as an intra-sample peak measure in dBFS.

The true peak maximum should never be larger than 0 dBFS. To decrease the true peak maximum by 1 dB, apply a gain of -1 dB to the audio signal.

One-click example

You can analyze the loudness of this song snippet with a simple click on this button:
Analyze Learn more The button is just a link with a specially constructed URL:
By requesting this URL, the input file will be imported into the system, processed by sonicAPI and the analysis result is displayed in your browser. The Live-Demo generates additional example code.

About the technology

The loudness analysis task uses the Metering technology by zplane.development, included in multiple audio software products such as zplane PPMulatorXL.