A Comparison Between Vapi and Other Voice AI Platforms
Introduction
Voice AI refers to the application of artificial intelligence technologies to enable systems to understand, process, and generate human speech. It allows users to interact with applications through natural language, which provides enhanced accessibility, productivity, and a better user experience.
As the demand for Voice AI grows with current technologies requiring high technical knowledge, Vapi has managed to fill in this gap through its state-of-the-art technology by allowing users to easily integrate Voice AI in their codebases. For users with limited programming skills, Vapi has a platform designed to help them build voice assistants through a quick and easy process.
This article aims to dig deeper into Vapi, its offerings, use-cases, as well as comparison with other similar tools.
Vapi
Vapi is a platform that enables developers to quickly build, test, and deploy voicebots. It is designed to make voice AI technology more accessible and easier to use for a wide array of applications that this article will discuss later on.
Vapi comes as a ready-to-go middleware layer where all the components (text-to-speech, speech-to-text, and natural language) have been integrated by its team. Through the Vapi API, developers can easily build their voice assistants, set up phone numbers, and place and receive calls. Furthermore, developers can either bring in their own language models or take advantage of third-party models that have already been integrated into Vapi.
Currently, Vapi costs $0.05 per minute in addition to any costs you may incur from your transcription, language, and voice models. This means that the cost of running Vapi will largely depend on the number and duration of the calls you expect to receive in a month along with the models you choose.
Vapi currently offers DeepGram as an integrated transcription service priced at $0.01 per minute. For language models, they offer gpt-4-turbo ($0.20/min) and gpt-3.5-turbo ($0.02/min). Several voice models are provided at the pricing below:
Estimated Prices of Voice Providers (USD)
However, you are free to use your own models or other third-party models by providing keys to the platform in order to integrate them.
Pricing Example
Let’s say your expected usage is around 10,000 minutes per month. You decide to use Deepgram ($0.01/minute), gpt-4-turbo ($0.20/minute), and PlayHT ($0.07/minute) for your transcription, language, and voice models respectively. This will result in a total cost of:
(10,000 * 0.05) + (10,000 * 0.01) + (10,000 * 0.20) + (10,000 * 0.07) = $3,300 per month.
To minimize the cost, developers can bring in their own models.
API Guide
To start using Vapi, you can simply sign up on their platform and set up a payment method. For API calls, be sure to include your private key that can accessed from the Account page. Here are some useful API calls to keep in mind when using Vapi. For the full list of calls, refer to Vapi’s official website.
| API Call | Description |
|---|---|
| Assistants | |
| POST /assistant | Create a new voice assistant |
| GET /assistant | Get a list of all your assistants |
| GET /assistant/{id} | Get a specific assistant |
| PATCH /assistant/{id} | Update an existing assistant |
| PUT /assistant/{id} | Replace an assistant |
| DELETE /assistant/{id} | Delete an assistant |
| Calls | |
| GET /call | List calls from assistant |
| GET /call/{id} | Get a specific call |
| POST /call/phone | Create a phone call |
| Phone Numbers | |
| POST /phone-number/buy | Buy a phone number |
| POST /phone-number/import/twilio | Import a Twilio number |
| POST /phone-number/import/vonage | Import a Vonage number |
| GET /phone-number | List phone numbers |
| GET /phone-number/{id} | Get a specific phone number |
| PATCH /phone-number/{id} | Update a phone number |
| DELETE /phone-number/{id} | Delete a phone number |
Vapi Features
Vapi offers many powerful features that make it a compelling platform for developers who are looking to incorporate voice AI technology in their applications. Here are some of the features that make Vapi a compelling choice:
Low Latency Conversations: Ensures real-time or near real-time interactions that make the interaction with the voicebot more natural.
Interruption-Detecting: Automatically detects when the user is interrupting the bot's speech, and therefore, stops generating output.
Scalable: Vapi is built to be scalable and is capable of supporting more than 1 Million concurrent calls at once.
Function-Calling: Allows the voicebot to access custom functions such as booking appointments, looking up data, and more.
Multilingual: Supports multiple languages that expand the potential user base by catering to non-English speakers.
Integration: Supports integration with your own models, voices, backends, and surfaces. Alongside this, it supports a number of built-in providers such as OpenAI for models and voices.
Pipedream API Integration: Allows users to easily build new voice assistants that perform custom actions with no coding required.
Use Cases
The features of Vapi pave the way for a wide array of use cases across industries, each of them leveraging voice AI to enhance user experience and streamline processes. Here are some of the use-cases that Vapi excels at:
| Use Case | Description |
|---|---|
| Customer Service | Handle routine customer inquiries, allowing human agents to focus on more complex issues and provide 24/7 support |
| Handle Bookings & Reservations | Handle incoming calls on dedicated phone numbers to make and modify appointments/bookings |
| Roleplay Training | Train new employees with voicebots dedicated to roleplaying certain situations in different contexts |
| Mock Interviews | Practice for upcoming job interviews with the AI and receive improvement tips |
| AI Companions | Engage in supportive and interactive emotional-support conversations |
| Voice IoT | Develop smart toys, home assistants, robots, cars, and smart mirrors |
| Educational Tools | Develop educating tools like language learning applications where users can practice new languages in real-time |
Tools Similar to Vapi
Bland AI
Bland AI is a platform that is focused on building AI phone calling applications at scale. It allows developers to easily send and receive phone calls using their API. It sets itself apart from Vapi by being the only infrastructure-level voice AI-building platform, which handles the entire end-to-end phone agent process itself without additional costs for external models. Some of the key features that bland offers are live call transfers, live context, and human-like voices - all at low latency.
Below is a comparison between Bland AI and Vapi:
| Feature | Bland AI | Vapi |
|---|---|---|
| Integration & Setup | Minimal coding required for integration | Easy development, testing, and deployment of voicebots that are suitable for non-technical users as well |
| Inbound Calls | Yes | Yes |
| Outbound Calls | Yes | Yes |
| API Access | Yes | Yes |
| Level of Solution | Infrastructure level | Middleware |
| Primary Focus | Providing groundwork for AI-powered phone systems - all in one | Facilitating development of voicebots and conversational AI features |
| Use Cases | Ideal for communications where live data injection is required such as healthcare | Customer service, e-commerce, smart home control, etc. |
| Customization | Voice selection, scenario creation, live function calls, host your own language model, and fine-tuning capabilities | Tools for conversational flow customization and support for multiple languages |
| Pricing | $0.12/minute | $0.05/minute + cost for phone numbers and models for transcription, LLM, and voice |
Bland AI users generally hit their rate limits at around 1000 calls per day. However, they offer solutions for enterprises through custom plans (100,000 + calls per day) that are provided after an initial demo. Response time data is not publicly available on their platform but they aim to deliver responses in under a second.
The key features that set Bland AI apart from Vapi include its level of solution, pricing, scalability, quality, and the ability to inject real-time data into phone calls rather than having predefined conversation flows. Bland AI is targeted towards enterprises that require scalable, high-performance voice AI solutions that can easily be integrated into their systems, whereas Vapi focuses on developer and businesses of all sizes looking to enhance their products with voice AI functionalities.
Retell AI
Retell API is a conversational voice AI API that helps developers integrate large language models with voice technology to create natural speech. Key features of Retell AI include realistic emotions, interruption handling, end-of-turn detection, and around 800ms latency for interactions. In addition to these, Retell also offers a playground to create an agent quickly without the need for coding skills.
Here is a comparison between Retell AI and Vapi:
| Feature | Retell AI | Vapi |
|---|---|---|
| Integration & Setup | Simplifies the process for developers to integrate their own LLMs with voice technology | Offers a platform for both technical and non-technical users to build, test, and deploy voicebots |
| Inbound Calls | Yes | Yes |
| Outbound Calls | Yes | Yes |
| API Access | Yes | Yes |
| Level of Solution | Middleware | Middleware |
| Primary Focus | Bridging the gap between speech-to-text, LLM, and text-to-speech technologies. | Facilitating the development of voicebots and conversational AI features |
| Customization | Extensive customization features like voice stability control, backchanneling, and addition of custom voices. | Customized conversational flows, multiple language support, and user-friendly design |
| Pricing | $0.10 - $0.12/minute + cost for phone numbers and LLM responses. | $0.05/minute + cost for phone numbers and models for transcription, LLM, and voice |
Comparison of Response Times (ms)
In addition to the prices labeled above, Retell charges an additional fee for enterprise plans (which support larger number of calls and increased support compared to only 10 concurrent calls for the pay-as-you-go plan). However, the plan includes a cheaper premium price, which can go as low as $0.05. The pricing of this plan is not available publicly and a demo must be booked in order to receive a quote.
Overall, Retell is focused more on the conversational aspect of voice AI to create human-like interactions, whereas Vapi provides a broader and cheaper platform for developing and deploying voicebots across various applications.
Air AI
Air AI is a conversational AI platform designed to conduct natural conversations through phone calls. It sets itself apart from its competitors through one of the features called “Genius Mode”, which is capable of keeping track of logic in calls with multiple people for longer than one hour. Through its API, Air AI can also be integrated with various applications that serve different purposes.
Here is a comparison between Air AI and Vapi:
| Feature | Air AI | Vapi |
|---|---|---|
| Infrastructure | Utilizes third-party LLMs for conversations | The middleware layer, integrates with company-owned models |
| Inbound Calls | Yes | Yes |
| Outbound Calls | Yes | Yes |
| API Access | Yes | Yes |
| Call Quality | Provides high-quality interactions but may be affected by third-party model performance | High-quality interactions but may face inconsistency due to external API dependencies |
| Primary Focus | Enable natural-sounding long phone conversations and integration with various applications | Facilitating the development of voicebots and conversational AI features. |
| Response Time | - | Around 500ms |
| Pricing | Outbound: $0.11/minute Inbound: $0.32/minute |
$0.05/minute + cost for phone numbers and models for transcription, language, and text-to-speech |
Conclusion
In this article, we have explored Vapi, a platform designed to streamline the development and deployment of voicebots, its use-cases, and a comparison to other platforms that offer similar technologies. Vapi, Bland AI, Retell AI, and Air AI not only demonstrate technological advancements in the field of Voice AI but also discover the potential that voice-enabled interfaces have for applications. Choosing one of these platforms comes down to your needs, technical expertise, and the size of your enterprise.
References
https://vapi.ai
https://www.retellai.com/
https://www.air.ai/
https://www.bland.ai/
https://www.bland.ai/blog/bland-ai-vs-retell-vs-vapi-vs-air#:~:text=Unlike%20platforms%20like%20Retell%20and,enable%20the%20best%20phone%20calls.
