> For the complete documentation index, see [llms.txt](https://docs.imerit.net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.imerit.net/labeling/labeling-editor-interface/audio-labeling-editor.md).
# Audio Labeling Editor
Ango Hub provides a labeling editor with which audio files can be annotated.
{% hint style="info" %}
This article will exclusively go over Ango Hub’s audio labeling interface. Features common to all labeling editors are instead [explained here](/labeling/labeling-editor-interface.md).
{% endhint %}
## Overview
### Supported File Types
The audio labeling editor supports audio assets with the following file extensions:
* .mp3
* .wav
* .ogg
### Supported Labeling Tools
The audio labeling editor supports following labeling tools:
**Tools**
* Entity
**Classifications**
* Radio
* Checkbox
* Single-Select Dropdown
* Multi-Select Dropdown
* Single-Select Tree
* Multi-Select Tree
* Text
**Relations**
* Single Relation
* Group Relation
### Audio Interface Elements
#### Playback bar
* allow you to move the playhead to the beginning of the audio file, five seconds back, play/pause, five second forward, and to the end of the file.
* The button becomes active when a segment is selected, and allows you to start playback starting from the beginning of the selected segment. (Pressing R on your keyboard will also enable this.)
* indicates the position of the playhead / the total duration of the audio file.
* When a segment is selected, allow you to move to the next/previous segment.
* If *Auto Scroll* is enabled, the list of segments below the playback bar will move with the playhead, always displaying as selected the currently playing segmentation.
* *Loop* repeats playback continuously. With no segment selected, it loops the entire audio asset. With a segment selected, pressing Play loops that segment; if the playhead is outside the segment, playback begins at the segment's start. Selecting a different segment while playback is active changes the loop target, and clearing the selection switches back to looping the full asset. Press G to turn Loop on or off.
* The icon enables you to pick a playback speed.
* The zoom slider enables you to pick a zoom level. You may also zoom in/out with the scroll wheel. Both types of zoom always zoom towards the current location of the playhead.
* The volume slider allows you to change the playback volume.
* Your playback speed and volume remain selected when you move to another audio asset using the navigation arrows, *Submit*, or *Skip*.
* The *Show Spectrogram* button displays a spectrogram below the waveform. The spectrogram uses the same timeline as the waveform, so playback, seeking, zooming, scrolling, and segment editing stay aligned across both views.
* For audio assets with more than one channel, the playback bar will also show a *Show Separate Channels* button. Clicking it displays each audio channel as a separate waveform, making it easier to inspect left and right channels independently.
* For stereo audio assets, the playback bar also includes a *Mixer* button. From the Mixer, you may move the stereo balance between *Left*, *Center*, and *Right*, or set an intermediate value with the slider. This allows you to lower one side of the audio and focus on the other channel while labeling.
#### Spectrogram View
The spectrogram view lets you inspect the frequency content of an audio asset while labeling. It appears under the waveform and can be shown or hidden from the playback bar.
When the spectrogram is visible:
* The waveform remains visible above it, unless you resize the panels to give the spectrogram the full available height.
* It uses a grayscale color scale to make differences in audio intensity easier to inspect.
* The frequency scale stays pinned on the left while you zoom and scroll through the audio. Select the settings icon in this gutter to choose the frequency range you want to inspect and adjust the analysis window. These settings are saved separately for each project.
* Hovering over the spectrogram shows the timestamp and approximate frequency under the cursor.
* Audio entity segments stay visible on both the waveform and spectrogram views.
To resize the waveform and spectrogram areas, drag the divider between them. The divider snaps between preset heights, letting you keep the waveform full size, shrink it, or hide it while keeping the spectrogram visible.
#### Top Bar
Click on the "Model Plugins" button to open a list of [model-type plugins](/plugins/plugin-developer-documentation.md) available in your organization.
If a [default preset](/plugins/introduction-to-plugins/plugin-configuration-and-preset-management.md) has been set for the plugin, the button will be clickable, and clicking on it once will run the plugin on the current asset with the default settings.
Clicking on the three dots next to the model name will open the Model Run Dialog, allowing you to customize the plugin's run settings and to run the plugin on the current asset with settings of your choice.
#### Segment List and Layered Text View
Use the view selector to switch between *Segment List* and *Layered Text View*. Ango Hub remembers the selected view after you reload the task.
The *Layered Text View* button is also available in the editor's right-side toolbar.
The *Segment List* allows you to see, at a glance, each segment currently present in the audio file. If segments have [nested classifications](/labeling/labeling-tools/tools/nested-classifications.md), those classifications will be displayed in the segment list. This can, for example, be a text classification, a dropdown, radio, or any other available [classification type](/data/importing-and-exporting-annotations/exporting-annotations/ango-export-format/asset/task/classifications.md).
*Layered Text View* organizes segments into numbered tiers. Select a tier to focus the waveform on its segments, then use the edit icon in a tier box to update its selection text. To move one or more selected segments to another tier, right-click them and choose *Change Tier*. New segments are added to the selected tier.
Clicking on the three dots next to each class's name will open a menu where you can open [object-specific issues](/core-concepts/issues.md#object-level-issues), or copy the unique Object ID of that object.
The `id` column displays a unique ID for the segment. These are the first three characters of the Object ID.
The *Classifications* column displays nested classifications of the class belonging to the segment, if any.
The *Start* and *End* columns display the timestamp when the segment starts and ends in the audio file. The *Duration* displays the duration of the segment.
If you hide an audio entity from the *Objects* panel using the eye icon, the same entity is also hidden from the waveform and from the *Segment List*. Hidden entities are skipped when using the next and previous segment controls. Showing the entity again from the *Objects* panel makes it appear in the waveform and *Segment List* again.
You may additionally delete the segment by clicking on the trash can.
## How to Annotate Audio
From the playback buttons on the bottom bar, start and stop playback of the audio file as necessary.
{% hint style="info" %}
If you get no sound, make sure that:
* Your system volume is on
* The volume slider on the bottom bar is not all the way to the left
* You have selected the right output device on your computer
{% endhint %}
From the *Tools* section on the left sidebar, select an *Entity* labeling tool, marked with an underlined *A* icon.
Click on the waveform where you’d like the annotation to start. Keep the left mouse button pressed and drag until where you’d like the annotation to end. Release the left mouse button.
You can change the start and end points of the annotation by selecting it with left-click, then dragging on one of the ends. You can drag the entire annotation by, after selecting it, clicking and dragging from the middle of the label.
To prevent audio entity annotations from overlapping, open the editor settings from the bottom-right corner of the editor. Choose *Prevent All Region Overlap* to prevent any overlap, or *Prevent Same-Class Region Overlap* to prevent overlap only between segments of the same class. Ango Hub remembers the selected overlap setting after reload.
When an overlap-prevention setting is enabled, newly drawn audio entity annotations cannot overlap according to the selected rule. If part of a new annotation would overlap an applicable existing annotation, Ango Hub shortens or moves its boundary to the nearest available range. If the new annotation is fully inside an applicable existing annotation, it is not created. Existing annotations follow the same rule when you edit their start or end points.
### Changing Audio Segment Opacity
To make the waveform easier to inspect behind audio entity segments, open the editor settings from the bottom-right corner of the editor and adjust the *Opacity* slider. The setting ranges from 0 (transparent) to 1 (opaque) and updates segment fills immediately in the waveform, separate-channel, and spectrogram views.
Selected segments remain slightly more visible than other segments. Issue regions and pending issue highlights keep their own visibility and are not changed by this setting.
Press `Y` to switch the opacity between 0 and the last non-zero value.
If the labeling tool has nested questions, right-click on the label and click on the menu that appears to see and answer the nested questions.
If classification questions are present, you may answer them from the *Questions* panel on the left sidebar.
## Opening Spot Issues
Besides issues about the asset as a whole and about individual objects, as outlined in the docs page on [issues](/core-concepts/issues.md), in audio assets you may also open 'spot' issues about specific timestamps or ranges of timestamps.
To do so, click on the *issue bubble* icon at the top-right of the screen. Then, either click once on the audio where you would like to open the issue, or click and drag on the audio waveform over the section of audio related to the issue:
## Merging two entities
Select multiple entities by holding Shift + clicking. Then, click on the "Merge" button that appears:
If the entities had attributes (nested questions):
* For all attribute types other than Text, only the attributes of the first entity are retained. (The first entity is the entity that starts first in the audio)
* For the Text attribute type, the text of the second entity is appended to the text of the first entity. (First and second refer to the timestamp at which the entities start in the audio.
## Keyboard Shortcuts
A list of keyboard shortcuts is available by clicking on the *Keyboard* button on the right side of the [top bar](/labeling/labeling-editor-interface.md#top-bar):
### Further reading
{% content-ref url="/pages/-Mjifco2debe91gXbTS1" %}
[Labeling Editor Interface](/labeling/labeling-editor-interface.md)
{% endcontent-ref %}