Voice API

Voice APIs allow developers to integrate voice calling, automated menus, and other convenient communication features into their apps without building them in-house, allowing them to focus on more pressing product concerns.

Let's explore voice APIs by looking at their features, benefits, how they work, and best practices for integrating them.

What Is Voice API?  

A voice Application Programming Interface (API) is a cloud-based collection of protocols and routines for integrating real-time voice communication features into an application.

With a voice API, companies can make calls with users on Voice over Internet Protocol (VoIP) devices or landlines and mobile phones through the Public Switched Telephone Network (PSTN).

Developers don't need to build calling functionality themselves; the company doesn't need to invest in expensive infrastructure or sign contracts with telecom companies.

Additionally, they can come with a range of supporting features, including:

• Interactive voice response (IVR)
• Number masking
• Number provisioning
• Answering machine detection (AMD)
• Speech-to-text 
• Text-to-speech
• Call recording 
• Call transcription

Voice APIs, sometimes called programmable voice APIs, might be standalone or offered alongside other communication APIs as part of a Communications Platform as a Service (CPaaS) solution.

They can enhance customer support, connect clients and service providers, facilitate internal communications, and improve user experiences.

For example, an online retailer can integrate a voice API, allowing customers to directly connect with support through their app or website.

The customer can use the company's automated IVR system to handle the call initially. They can use speech or the number pad to navigate a custom menu. If their needs aren't met, they can be redirected to a live agent.

How Do Voice APIs Work?

The voice API provider handles the infrastructure, call logic, call routing, initiating and terminating connections, and supporting features.

All you need to do is integrate the API into your product.

Let's dive deeper into how this works.

At a minimum, the API request for making an outbound call contains the API key, the recipient's phone number, and the sender's number. More intricate requests may contain fields like:

• Display names
• Instructions for call recording, transcription, text-to-speech, AMD, and/or audio playback
• Codec information
• Timeout limits

If the call is placed successfully, you'll receive an API response with a 200 code and information like the call status and session ID.

Throughout the call, the provider's server will send you webhooks with call and recording status, duration, costs, rates, timestamps, and other related data.

Developers can set responses to specific webhooks to help guide the call, initiate recording or transcription, respond to user speech or dial tone input, play hold music, or convert text-to-speech.

Behind the scenes, the Session Initiation Protocol (SIP) signals the start and end of calls between endpoints. Endpoints can be web or mobile apps, landlines, mobile phones, and other devices.

SIP is also responsible for tasks such as:

• Checking if an endpoint is available
• Ringing the device
• Assessing which codecs to use

Most importantly, SIP trunks bridge your endpoints with your customers' devices, whether they use SIP, WebRTC, or are on the PSTN. You create SIP trunks on the provider's servers, which are capable of handling several concurrent calls. When demand increases, you create another trunk and procure more numbers to meet demand.

The actual voice data transfer happens with Real-Time Transport Protocol (RTP) or Secure Real-Time Transport Protocol (SRTP).

Voice APIs come loaded with features that can enhance customer experience during calls and capture and analyze important call data.

Common Features of Voice APIs

The available features will vary by provider, but some of the most common include:

• Inbound and outbound calling: The API enables domestic, international, and internet calls.
• Conference calling: Calls can have three or more participants.
• Number provisioning: You can acquire local or toll-free numbers for the countries and specific locales in which you operate.
• Software development kits (SDKs): Language- and platform-specific tool kits that speed up client-side communication implementation.
• Number masking: A way to protect callers' identities by obscuring their real phone numbers. For instance, a customer service employee can field a call from their cell phone, but the number shows up as the company's number instead of their own.
• Speech-to-text (STT): Voice recognition that converts a speaker's utterances into text, enabling menu navigation, call transcriptions, payments, and other interactions.
• Text-to-speech (TTS): Computer-synthesized speech for automating things like alerts and notifications. TTS is available in multiple languages and dialects.
• Noise suppression: Automated background noise reduction for better sound quality.
• End-to-end encryption: SRTP and transport layer security (TLS) to keep voice data safe from bad actors.
• Interactive voice response (IVR): Automated menu system for handling simpler segments of user phone calls. You can use it for customer service, surveys, payments, routing calls, and more to free up time for your human representatives.
• Voice bots: Bots that combine natural language processing, STT, and TTS to handle open-ended customer conversations that are too complex for IVR.
• Analysis tools: AI-powered tools that comb through call transcriptions to gain insights from data like customer sentiment, call duration, and key terms used in a conversation.

What Are the Benefits of Using a Voice API?

Besides the advantages derived from the features, there are a host of benefits when using a voice API for developers, other employees, and customers, such as:

Cost and Time Savings

Voice APIs speed up development significantly. Developers don't need to worry about the complicated logic needed to handle the different aspects of calling. Instead, they just integrate the API as guided by the provider, freeing them up to spend their time on more business-critical tasks.

With the use of IVR and analytics, marketing, support, and other teams can glean valuable customer and employee information to improve metrics like sales, customer satisfaction, and agent performance.

Scalability and Reach

The provider's cloud infrastructure powers your communications. Businesses don't need to invest in the infrastructure or set up contracts with international telecom companies. They can scale up or down as needed by provisioning more numbers and adding more concurrent calls and SIP trunks.

Better User Experience

In-app communication is not only convenient, but it's something that customers have come to expect from the companies they buy from.

Whether calling a telemedicine provider to ask about a prescription, a rideshare driver to arrange a pickup, or an ecommerce support member to discuss shipping options, voice APIs provide speed and convenience that boost user experience and aid in retention.

Best Practices for Voice API Implementation

You should follow these best practices when selecting an API and setting it up:

Pick the Right Provider

Before signing a contract, consult with your team on what factors matter most for your business and keep those in mind as you shop around for vendors.

Providers will differ by features, the countries they cover, the languages they support, pricing, and the strength of their customer support. Some let you use your existing carrier, whereas others may want you to use their networks exclusively.

Consult with customer reviews from companies with use cases similar to yours. Determine if there are any concerns for poor customer service, high latency, dropped calls, poor audio quality, and any other issues.

Follow Standard Security Practices

Phone conversations can involve vulnerable information, such as health conditions, payment details, and home addresses.

To secure customer and employee data, you should configure your API settings to encrypt voice data, transcriptions, and recordings.

You should also safeguard your API key by keeping it on a separate server or somewhere else secure to prevent malicious parties from abusing it or committing fraud.

Some vendors offer IP-based access control lists or allow you to require login credentials for incoming SIP traffic to keep unauthorized users out of your systems.

Prioritize Compliance

Adhere to the calling regulations in your industry, country, and region. Your vendor can help, but much of the work falls on your company.

For instance, telemedicine companies that follow HIPAA guidelines must have their API provider sign a business associate agreement (BAA) outlining how they will safeguard patients' protected health information (PHI). Each company must configure the API to be compliant, which will involve measures such as following proper security measures, training staff, and performing risk assessments.

Frequently asked questions