Playing audio in call


Functionality described in this document is currently in public preview. This preview version is provided without a service-level agreement, and it's not recommended for production workloads. Certain features might not be supported or might have constrained capabilities. For more information, see Supplemental Terms of Use for Microsoft Azure Previews.

The play action provided through the call automation SDK allows you to play audio prompts to participants in the call. This action can be accessed through the server-side implementation of your application. The play action allows you to provide ACS access to your pre-recorded audio files with support for authentication.


ACS currently only supports WAV files formatted as mono channel audio recorded at 16KHz. You can create your own audio files using Speech synthesis with Audio Content Creation tool.

The Play action allows you to provide access to a pre-recorded audio file of WAV format that ACS can access with support for authentication.

Common use cases

The play action can be used in many ways, below are some examples of how developers may wish to use the play action in their applications.


Your application might want to play some sort of announcement when a participant joins or leaves the call, to notify other users.

Self-serve customers

In scenarios with IVRs and virtual assistants, you can use your application or bots to play audio prompts to callers, this prompt can be in the form of a menu to guide the caller through their interaction.

Hold music

The play action can also be used to play hold music for callers. This action can be set up in a loop so that the music keeps playing until an agent is available to assist the caller.

Playing compliance messages

As part of compliance requirements in various industries, vendors are expected to play legal or compliance messages to callers, for example, “This call will be recorded for quality purposes”.

Sample architecture for playing audio in a call

Screenshot of flow for play action.

Known limitations

  • Play action isn't enabled to work with Teams Interoperability.

What's coming up next for Play action

As we invest more into this functionality, we recommend developers sign up to our TAP program that allows you to get early access to the newest feature releases. Over the coming months the play action will add new capabilities that use our integration with Azure Cognitive Services to provide AI capabilities such as Text-to-Speech and fine tuning Text-to-Speech with SSML. With these capabilities, you can improve customer interactions to create more personalized messages.

Next Steps

Check out our how-to guide to learn how-to play custom voice prompts to users.