Speech-to-text (also known as speech recognition or voice recognition) is a technology that converts spoken language into written text. It’s the digital ears that listen and the virtual hands that type to translate our voices into words on a screen. This seemingly simple concept opens up a world of possibilities, from making our daily lives more convenient to transforming entire industries.
Imagine:
Drafting emails while stuck in trafficTranscribing meetings without furiously scribbling notesProviding real-time captions for videos and real-time events
These are just a few examples of how speech-to-text is changing life and work for individuals and businesses.Â
Whether you’re a curious individual looking to boost productivity or a business leader seeking to innovate, speech-to-text can change the way you get things done in today’s voice-first world.Â
This complete guide to speech-to-text will walk you through everything you need to know about this technology, including: what it is, how it works, and why we need it.Â
What is speech-to-text technology?
Speech-to-text technology is a sophisticated system that converts spoken words into written text. It’s the bridge between the auditory world of human speech and the visual world of written language that enables machines to understand and transcribe spoken language.
Speech-to-text technology relies on a combination of linguistics, computer science, and artificial intelligence to function. Here’s a simplified breakdown of how one exemplary type of speech-to-text model works:
Audio Input: The system receives an audio signal, typically from a microphone or an audio file.Signal Processing: The audio is preprocessed for transcoding and audio gain normalization.Deep Learning Speech Recognition Model: The audio signal is fed into a speech recognition deep learning model trained on a large corpus of audio-transcription pairs, which generates the transcription of the input audio.Text formatting: The raw transcription generated by the speech recognition model is formatted for better readability. This includes adding punctuation, converting phrases like “one hundred dollars” to “$100,” capitalizing proper nouns, and other enhancements.
Modern speech-to-text systems often use machine learning algorithms (particularly deep learning neural networks) to improve their accuracy and adapt to different accents, languages, and speech patterns.
Types of speech-to-text engines
There are several types of speech-to-text engines to consider, each with its own advantages, disadvantages, and ideal use cases.
The right choice for you will depend on your needs for accuracy requirements, language support, integration capabilities, and data privacy concerns.
Cloud-based vs. on-premise
Cloud-based: These systems process audio on remote servers, offering scalability and no infrastructure maintenance. They’re ideal for businesses handling large volumes of data or requiring real-time transcription. On-premise: These systems run locally on the user’s hardware and can function without internet connectivity. The cost is sometimes less than cloud-based, however, initial costs for hardware and ongoing costs of maintenance and support staff can negate these savings.
Learn more about cloud-based security measures
Open-source vs. proprietary
Open-source: These engines allow users to view and sometimes modify and distribute the source code, though with specified limitations. They offer flexibility and customization options but may require more technical expertise to implement and maintain.Proprietary: Developed and maintained by specific companies, these systems can be tailor-made for specific use-cases, such as industry-relevant audio as we do. Look for proprietary engines that are also continuously updated.
How does speech-to-text work?
Understanding the deeper technical processes helps you appreciate the complexity behind the seemingly simple conversion of speech into text and why factors like audio quality and accents can affect the accuracy of this process.
1. Audio Preprocessing
Before any analysis can begin, the audio input needs to be converted into a format usable by a speech recognition deep learning model. This involves:
Transcoding: Change the audio format to a standard form (See best audio file formats for speech-to-text). Normalization: Adjusting the volume to a standard level.Segmentation: Breaking the audio into manageable chunks.
2. Deep Learning Speech Recognition Model
This process maps the audio signal to a sequence of words. Modern systems use end-to-end deep learning models, such as Transformer and Conformer. The Conformer model is an enhanced version of the Transformer, designed to better capture speech dynamics, making it particularly suitable for speech recognition. The model is trained on a large dataset of audio-text pairs to learn the mapping from the audio signal to the corresponding transcription. The model implicitly acquires and utilizes knowledge of how each word should sound and how different words are likely to connect to form a sentence.
To be more precise, the model usually generates the likelihood of each word—or linguistic unit—being spoken for each short time frame. A program called a decoder then generates the most probable word sequence based on the per-linguistic-unit likelihood values produced by the deep learning speech recognition model.
3. Text Formatting
The word sequence generated by the deep learning speech recognition model often does not have punctuation and is all lowercase. Also, entities, such as emails, URLs, and numbers, are typically spelled out. The final step converts the raw word sequence generated by the speech recognition model into a more readable text format. This often involves processes called inverse text normalization, capitalization, and true-casing, and they are accomplished by using rule-based algorithms or text processing neural network models.Â
Factors affecting speech-to-text accuracy
While that might sound relatively straightforward, there are a few factors that can muddy up audio files and impact the accuracy of speech-to-text systems:
Audio quality: Clear, high-quality audio with minimal background noise yields the best results. Poor microphone quality or low bitrate audio can significantly reduce accuracy.Accents and dialects: Systems trained on a specific set of accents may struggle with others. Background noise and reverberation: Ambient sounds and room reverberation can interfere with speech recognition. Noise cancellation using microphone arrays often results in improved speech recognition accuracy, whereas the usefulness of monaural noise reduction systems is not well established.Speaking style: Clear, well-enunciated speech is easier to recognize. Rapid speech, mumbling, or overlapping voices can challenge the system.Vocabulary: Uncommon words, technical jargon, or proper nouns may be misrecognized. Some systems allow for custom vocabulary to improve accuracy in specific domains.Language and context: Multi-language environments can be challenging. Understanding context helps in disambiguating similar-sounding words.Speaker variability: Differences in pitch, speed, and vocal characteristics can affect accuracy. Some systems can adapt to individual speakers over time.
Benefits of speech-to-text technology
Speech-to-text technology provides major advantages for both individuals and businesses across various industries. And, it’s still in its relative infancy — we’re sure to see even more innovative applications and benefits as users continue to adopt and innovate with speech-to-text.
Increased productivity: Speech-to-text can reduce time spent on manual transcription and note-taking.Improved accessibility: This technology provides support for individuals with hearing impairments, mobility issues, or learning disabilities.Better customer experiences: Businesses using speech-to-text in customer service operations can reduce average handling time and improve first-call resolution rates.Cost reduction: Automated transcription can be cheaper than human transcription services and allows businesses to reallocate resources to more complex, high-value tasks.Better data analysis: Speech-to-text enables more efficient analysis of large volumes of data (leading to more informed decision-making).Improved compliance and record-keeping: Speech-to-text provides accurate documentation of conversations and meetings.Flexibility and convenience: This technology can be used across various devices and integrated with existing software to offer users flexibility in how and where they work.
Applications of speech-to-text technology
Speech-to-text technology has found its way into several applications across various industries and personal use cases. You might have even already used it today without even thinking about it (like with Siri or Alexa).Â
Here are a few of the most prominent applications and real-world examples for personal and business use:
Personal use case
Dictation and note-taking: Students and professionals use speech-to-text to quickly capture ideas, create documents, or take notes during lectures and meetings. For example, a journalist might use speech-to-text to transcribe interviews in real time, saving hours of manual transcription work.Accessibility: Speech-to-text provides support for individuals with hearing impairments. It enables real-time captioning of live events, phone calls, and video content to make information more accessible.Voice commands and virtual assistants: Speech-to-text powers virtual assistants (like Siri, Alexa, and Google Assistant) that allow users to set reminders, send messages, or control smart home devices using their voice.
Business applications
Customer service and call centers: Many companies use speech-to-text to transcribe customer calls automatically. This allows for easier analysis of customer interactions, identification of common issues, and improvement of service quality.Meeting transcription: Businesses use speech-to-text to create searchable archives of meetings and conferences. This helps with record-keeping, allows absent team members to catch up, and makes it easier to reference important discussions later.Content creation: Podcasters and video creators use speech-to-text to generate accurate transcripts and subtitles for their content to improve accessibility and SEO.Legal and medical transcription: Law firms and healthcare providers use specialized speech-to-text systems to transcribe depositions, court proceedings, and medical notes.
Real-world examples of speech-to-text technology
Jiminny in sales and customer success
Jiminny, a Conversation Intelligence platform, uses AssemblyAI’s speech-to-text technology to power its sales coaching and call recording features. This integration helps Jiminny’s customers secure a 15% higher win rate on average by providing AI insights for data-driven coaching that improves forecasting accuracy and customer knowledge.
Marvin in user research
Marvin, a qualitative data analysis platform, integrated AssemblyAI’s Core Transcription and PII Redaction models into their user research tools. This implementation helps Marvin’s users spend 60% less time on average analyzing data, allowing them to focus more on extracting meaningful insights from customer interviews and feedback.
Screenloop in hiring intelligence
Screenloop, a hiring intelligence platform, embedded AssemblyAI’s transcription model into their interview process tools. This integration resulted in significant improvements for Screenloop’s customers, including 90% less time spent on manual hiring tasks, 20% reduced time-to-hire, 60% less candidate drop-off, and 50% fewer rejected offers for open roles.
How to choose the right speech-to-text tool
Not every speech-to-text solution is going to be the right fit for your business and its use case.Â
Here are few factors to consider to narrow down the best tool for your needs:
Accuracy: Look for tools with high transcription accuracy rates. State-of-the-art models like AssemblyAI’s Universal-1 achieve near-human-level performance across a wide range of data.Language support: Consider whether the tool supports the languages you need. Some solutions offer multilingual capabilities, while others specialize in specific languages or dialects.Pricing: Compare pricing models (pay-as-you-go, subscription-based, etc.) and guarantee they align with your usage patterns and budget.Integration options: Check if the tool easily integrates with your existing systems and workflows. APIs and SDKs can facilitate seamless integration.Customization capabilities: Look for features like custom vocabulary or acoustic model adaptation that can improve accuracy for your specific use case.Processing speed: Consider both real-time transcription capabilities and batch processing speeds for pre-recorded audio.Additional features: Evaluate extra functionalities like speaker diarization, punctuation, sentiment analysis, or content summarization.Security and compliance: Double-check that the tool meets your data security requirements and complies with relevant regulations (like GDPR and HIPAA).Scalability: Choose a solution that can handle your current needs and scale as your requirements grow.Support and documentation: Consider the level of technical support and the quality of documentation provided by the vendor.
Tool
Key Features
Pros
Cons
Pricing
AssemblyAI
• State-of-the-art accuracy
• Real-time & async transcription
• Advanced AI features
• Highly accurate
• Comprehensive API
• Excellent support
• API-focused
• Free tier: $50 credits
• Pay-as-you-go: From $0.12/hr
Google Cloud Speech-to-Text
• 125+ languages
• Noise cancellation
• Google Cloud integration
• Wide language support
• Reliable & scalable
• Complex for beginners
• Less competitive for high volume
• Free: 60 min/month
• Standard: $0.016/min
• Medical: $0.078/min
Amazon Transcribe
• Real-time & batch
• Custom vocabularies
• AWS integration
• AWS integration
• Scalable
• AWS learning curve
• Limited advanced features
• Free: 60 min/month for 12 months
• Standard: $0.0258/min
• Real-time: $0.0402/min
Popular speech-to-text tools
1. AssemblyAI
AssemblyAI is a powerful, developer-friendly speech-to-text API that leverages cutting-edge AI models to provide accurate transcription and advanced audio intelligence features. It offers both streaming (real-time) and asynchronous transcription capabilities — making it reliable for a wide range of applications from live captioning to post-production content analysis.
Features:
State-of-the-art accuracy with Universal-1 modelStreaming (real-time) and asynchronous transcriptionCustom vocabulary Speech Understanding: Speaker diarization, sentiment analysis, content summarization, topic detection, and moreMultilingual support
Pros:
Highly accurate transcriptionsComprehensive API with advanced AI featuresExcellent documentation and customer supportFlexible pricing for various usage levels
Cons:
Primarily focused on API integration — may not be ideal for non-technical users
Pricing:
Free tier: $50 in free creditsPay-as-you-go: As low as $0.12/hrCustom: Personalize your plan
2. Google Cloud Speech-to-Text
Google Cloud Speech-to-Text is a cloud-based speech recognition service that converts audio to text using Google’s machine learning technology. It offers a wide range of language support and integrates seamlessly with other Google Cloud services, making it a versatile choice for businesses already using the Google ecosystem.
Features:
Real-time and asynchronous transcriptionSupport for 125+ languages and variantsNoise cancellation and speaker diarizationIntegration with other Google Cloud services
Pros:
Wide language supportGood integration with Google ecosystemReliable and scalable
Cons:
Can be complex for beginnersLess competitive pricing for high-volume usersLower accuracy
Pricing:
Free tier: First 60 minutes per monthStandard recognition: $0.016 per minute for the first 500,000 minutes/month, with tiered pricing for higher volumesMedical models: $0.078 per minute after the free 60 minutes/monthDynamic batch recognition: $0.003 per minuteDiscounted rates available for data logging options
3. Amazon Transcribe
Amazon Transcribe is a cloud-based automatic speech recognition (ASR) service that makes it easy for developers to add speech-to-text capability to their applications. As part of the AWS ecosystem, it offers seamless integration with other Amazon services and provides both real-time and batch transcription options.
Features:
Real-time and batch transcriptionCustom vocabulary and language modelsAutomatic language identificationSpeaker diarization and channel separationIntegration with AWS ecosystem
Pros:
Seamless integration with AWS servicesGood accuracy for common use casesScalable for large-volume transcription needs
Cons:
Learning curve for AWS environmentLimited advanced AI features compared to specialized providersHigh costLimited accuracy for more specialized use cases
Pricing:
Free tier: 60 minutes of transcription per month for the first 12 monthsStandard transcription: $0.00043 per second ($0.0258 per minute)Real-time transcription: $0.00067 per second ($0.0402 per minute)
The future of speech-to-text technology
Speech-to-text technology is poised for exciting advancements, especially with the current evolution and progress of artificial intelligence research.
We can expect to see improvements in accuracy in challenging environments with background noise or multiple speakers. AI-powered features like emotion detection, intent recognition, and more sophisticated language understanding will likely become standard, improving the technology’s ability to capture context and meaning beyond written words.
New applications will emerge across industries. In healthcare, more accurate medical transcription could improve patient care and streamline documentation. Education might see personalized learning experiences based on real-time speech analysis. Customer service could benefit from advanced sentiment analysis and automated response suggestions.
However, it’s not necessarily a straight and obstacle-free road ahead — challenges remain. Privacy concerns and data security will be ongoing issues as these systems process increasingly sensitive information. There’s also the risk of bias in AI models, which could lead to unequal performance across different demographics or accents.
Unlock the power of speech-to-text with AssemblyAI
Speech-to-text technology has revolutionized how we interact with devices, create content, and process information. However, you’re not just a user of this technology — you can be a builder.
AssemblyAI provides a powerful, developer-friendly speech-to-text API that leverages cutting-edge AI models. It provides both streaming (real-time) and asynchronous transcription capabilities for a variety of applications. You also get access to features like:
Custom vocabulary for improved accuracy in specific domainsAdvanced AI models like speaker diarization, sentiment analysis, and content summarizationMultilingual support for global applicationsExcellent documentation and customer support for smooth integration
Try AssemblyAI today to experience the future of speech recognition technology
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