Audio Call

From voice notes to in-app conversations, real-time audio is everywhere.

Behind every clear, low-latency voice call is a set of technologies working together to deliver that seamless experience. What feels instant to users is actually the result of careful coordination across devices, networks, and software layers.

What is an Audio Call?

An audio call is a real-time voice communication session between two or more people, transmitted over a network using technologies like VoIP (Voice over Internet Protocol) or cellular networks. Unlike text-based communication, audio calls provide immediate, synchronous interaction through spoken language.

Audio calls can be initiated in a variety of environments:

Traditional Phone Lines: Rely on circuit-switched networks, like the Public Switched Telephone Network (PSTN), to transmit voice between callers.
Internet-Based Systems: Transmit voice data as digital packets over IP networks, offering more flexibility and cost efficiency.
In-App SDKs: Modern mobile and web apps often include audio functionality powered by SDKs that use WebRTC, a framework built into browsers and mobile devices, or other real-time protocols.

How Do Audio Calls Work?

Audio calling hinges on a series of software processes and network protocols designed to capture, transmit, and render voice in real time with minimal delay or distortion.

Key Components

Capture & Encoding: The user's microphone captures their voice. That signal is compressed using audio codecs like Opus (designed for interactive speech) or G.711 (commonly used in PSTN).
Transport Layer: Compressed voice data is transmitted using protocols like Real-time Transport Protocol over User Datagram Protocol, which prioritizes low latency. WebRTC streamlines this process for developers.
Decoding & Playback: Once received, the voice data is decompressed and played through the recipient's speaker or headphones.

Call Types

Peer-to-Peer (P2P): Direct device-to-device audio streaming. Ideal for one-on-one conversations.
Server-Routed: Media servers either route audio streams using a Selective Forwarding Unit or mix them with a Multipoint Control Unit—both essential for multi-party calls.

Technologies Behind Audio Calls

VoIP: Sends voice over internet-based IP networks. It's the backbone of most modern calling apps.
WebRTC: A developer-friendly, browser-native framework that supports real-time audio (and video) without plugins.
Call SDKs: In-app voice calling SDKs make it easy to integrate real-time audio with prebuilt infrastructure, reducing time-to-market and complexity.

Use Cases for Audio Calls

Audio calls are a versatile communication tool embedded in countless digital experiences. Here are some of the most common scenarios:

Healthcare

Telehealth platforms increasingly rely on audio calls for voice-based consultations, particularly when video isn't necessary or available.

Audio reduces bandwidth requirements and makes care more accessible, especially for users on mobile devices or in low-connectivity regions. Developers need to ensure HIPAA compliance, integrate secure signaling, and support mobile-friendly UX for quick voice check-ins.

Gaming

In fast-paced, multiplayer games, audio supports real-time strategy, team coordination, and immersive gameplay. In-game voice must be low latency and support features like push-to-talk, spatial audio, and mute controls.

Many game developers use peer-to-peer or server-based audio channels integrated directly into the game engine or a third-party SDK.

Customer Support

Businesses often embed voice calling into their support apps to offer real-time help without the overhead of video.

It's particularly useful for mobile-first or asynchronous customer support tools. Developers implementing this use case should consider call queuing, call recording, and easy handoff between chat and voice channels.

Audio-first social features, like Clubhouse-style drop-in rooms or private 1:1 calls, are now standard in messaging and community apps. These features let users connect in a more authentic, spontaneous way without the pressure of video.

For developers, this means building scalable, server-routed audio that can support many concurrent users, real-time moderation, and speaker/host controls.

Collaboration Tools

Collaboration apps like Slack, Discord, and Microsoft Teams use audio calling for daily standups, brainstorming sessions, or just staying connected while working.

Audio offers a hands-free, low-friction way to stay in sync. Developers working on this use case should prioritize features like persistent audio channels, device switching (e.g., from desktop to mobile), and seamless transitions from chat to voice.

Technical Considerations

To deliver a seamless and reliable experience across platforms and network conditions, developers account for several factors:

Latency and Jitter

Low latency aids natural, conversational voice calls. Aim for smooth delivery by using real-time audio protocols and adaptive codecs. Most modern SDKs handle this behind the scenes, managing buffering, packet timing, and bitrate adjustments.

Echo Cancellation and Noise Suppression

Mobile and browser environments often involve built-in microphones and speakers, which are prone to echo and background noise. Built-in features like echo cancellation and noise suppression keep audio clear, especially in mobile or speakerphone scenarios.

Network Fallback or Reconnection Logic

Users move between networks, lose connectivity, and switch from Wi-Fi to cellular. Your calling experience should recover gracefully. Automatic reconnection and smart fallback logic ensure that short drops don't end the conversation.

Cross-Platform Support (iOS, Android, Web)

Your audio calling experience should be seamless regardless of platform. That means consistent handling of permissions, background behavior, and UI, from mobile to browser. Using a cross-platform SDK helps reduce friction and ensures parity.

Frequently Asked Questions

What’s the Difference Between Audio Calls and Video Calls?

Audio calls transmit only voice, while video calls include both voice and visual data from a camera. Audio is lighter on bandwidth, faster to connect, and often better suited for mobile or on-the-go communication. If your app doesn’t require face-to-face interaction, audio is usually the simpler, more battery-efficient option.

What Are FaceTime Audio Calls?

FaceTime audio is Apple’s voice-only calling feature that works over the internet instead of a phone line. It uses VoIP technology to provide high-quality audio, especially over Wi-Fi or strong cellular networks. Think of it as a data-based phone call between Apple devices.

What Is an Audio Message on My Phone?

An audio message is a short, recorded voice clip you can send via messaging apps. Unlike a real-time call, it’s asynchronous—more like voice texting. Users often send them when it’s faster or easier to talk than type.

What Is an Audio Call on Facebook Messenger?

An audio call on Facebook Messenger is a real-time voice call made over the internet using the Messenger app. Like other VoIP-based calls, it works over Wi-Fi or cellular data and doesn’t require a phone number. Messenger also lets you switch to video or group calls seamlessly.

What Is an Audio Call on Instagram?

Instagram offers voice calling through DMs, letting users start audio chats without leaving the app. It’s a lightweight way to connect, especially for casual conversations between followers. Like Messenger, it uses internet data rather than traditional phone service.

How Can I Add Audio Calling to an App?

You can integrate audio calling using a real-time communication SDK. These SDKs handle complex tasks like signaling, media transport, and cross-platform behavior, so you don't have to build it all from scratch. With the right setup, you can launch a functional, scalable audio experience in days instead of months.