Useful column: Voice recognition
Useful column: Voice recognition
October 6, 2025
Basic knowledge and usage of speech recognition API

Basic knowledge of speech recognition API
What is a speech recognition API?
A speech recognition API is an interface for converting human speech into text. An API (Application Programming Interface) is a mechanism for different software programs to work together, and a speech recognition API provides the functionality to analyze voice data and output it as text information.
This technology allows developers to easily incorporate speech recognition functionality into their applications, enabling users to control and input using their voice simply by speaking into a microphone. It has a wide range of applications, including automatic subtitle generation for videos, analysis of emotional speech, and vocabulary learning support.
Representative speech recognition APIs include the following services:
Google Cloud Speech-to-Text
It provides highly accurate speech recognition in real time, supports multiple languages, and excels at transcribing video and audio files.
IBM Watson Speech to Text
It enables more advanced analysis, such as identifying emotions and speakers, and is increasingly being used for business purposes.
These services differ not only in the accuracy of speech recognition, but also in the number of languages they support, the richness of their vocabulary, and the ease of use of their APIs, so it is important to choose one that suits your purpose.
It is expected that speech recognition APIs will continue to evolve in the future and be used in a variety of fields as a technology that provides a deeper understanding of human expressiveness and emotions.
How voice recognition works
Speech recognition is a technology that automatically converts speech into text, and is achieved through several steps. Here we will explain the basic process in an easy-to-understand manner.
1. Acquiring the audio signal
The user's voice is captured through an input device such as a microphone. Since voice is originally an analog signal, it is converted into a digital signal so that it can be processed by a computer. During this process, preprocessing such as removing environmental noise and optimizing the volume is performed, which greatly contributes to improving the accuracy of voice recognition.
2. Audio Processing
The digitized speech is then analyzed by an acoustic model, which extracts features such as frequency and intensity of the speech and associates them with words and vocabulary. A language model then selects the most natural representation based on the context and outputs the final text.
3. The Role of Machine Learning
Machine learning engines are deeply involved in this entire process. The algorithms are trained based on large amounts of audio data, enabling highly accurate recognition that takes into account differences in pronunciation, speaker habits, and even the relationship with speech synthesis. Continuous learning is essential, especially in order to understand differences in emotions and speaking styles.
As you can see, speech recognition is not simply a matter of converting speech, but rather a system that combines complex processing and advanced technology. Understanding this process will help you better appreciate the value and potential applications of speech recognition APIs.
Voice Recognition API Use Cases
Business Edition
In recent years, business applications for speech recognition APIs have expanded rapidly. Developers are incorporating speech recognition technology into a variety of applications to improve business efficiency and customer satisfaction. Here we introduce some typical use cases.
Streamlining customer support
Call centers and customer support systems can use speech recognition APIs to capture customer speech in real time and convert it into text. This allows operators to quickly understand the content of the inquiry and provide an appropriate response. In addition, saving and analyzing past response history as a file can also lead to improved service quality.
Taking meeting minutes
In business, it is important to accurately record the contents of meetings. Using a speech recognition API, you can automatically transcribe what is said during meetings, making the creation of meeting minutes more efficient. This eliminates the need for manual recording and saves time. Furthermore, registering technical terms in advance allows for more accurate recognition.
Strategy planning through voice data analysis
Speech recognition APIs can be used not only for transcription but also for analyzing voice data. Needs and trends can be identified from conversations with customers, and this information can be used for marketing and product development. For example, by extracting frequently occurring terms and expressions, you can understand customer interests and provide more effective services.
As you can see, speech recognition APIs are being used in a variety of business situations and are becoming an important technology that can increase a company's competitiveness. By trying it out, you can experience its benefits for yourself.
Education
Speech recognition APIs are also used in many areas in the field of education. In particular, they are attracting attention as a technology that contributes to improving the efficiency of lessons, learning support, and the quality of education. Here we will introduce some specific use cases.
Lecture recording and transcription
By recording audio during class and automatically transcribing it using a speech recognition API, students can easily review the content of the class later. This is particularly useful for checking pronunciation and expressions in language learning classes such as English. Teachers can also obtain lesson records as information and use it to improve their teaching content.
Language learning support
Speech recognition APIs are also powerful tools in language education, such as English language learning. They recognize what students say in real time and provide feedback on pronunciation accuracy and grammar usage, supporting continuous learning. This is especially true for pronunciation and conversation practice, as it saves teachers the trouble of having to meticulously check each student's speech, making instruction more efficient.
Analysis of student comments
By recording and analyzing what students say during class, it is possible to understand factors such as their level of participation and understanding. Using a speech recognition API, it is possible to automatically record who said what and use this data to improve the quality of education. This allows teachers to adjust the way they teach classes and provide more effective education.
There are many benefits to using speech recognition APIs in the education field, and it is expected that they will be used in even more schools and educational institutions in the future.
Points to note when introducing speech recognition API
Speech recognition APIs are extremely useful technology, but there are some important points to keep in mind when implementing them. Understanding these beforehand will ensure smooth operation and high effectiveness.
1. Terms of Use and Privacy Policy
When introducing a speech recognition API, be sure to check the service provider's terms of use. In particular, information regarding the acquisition, storage, and sharing of voice data must be managed with care. If personal or confidential information is included, operations must be conducted in accordance with laws, regulations, and company rules.
2. Suitability for the target environment
It is also important to check whether the API you are introducing is suitable for the actual environment in which it will be used. For example, recognition accuracy may decrease in noisy places or situations where multiple people are speaking at the same time. It is necessary to conduct a trial introduction in advance and adjust it according to the environment.
3. Support for terminology and technical vocabulary
If your industry uses a lot of jargon or abbreviations, make sure your speech recognition API can correctly recognize them. Many services allow you to add custom vocabulary, which can improve recognition accuracy.
4. Integration with applications
Speech recognition APIs are more effective when integrated with existing business applications and systems, rather than used on their own. Before implementing an API, it is important to check the technical requirements and ensure it is compatible with your company's systems.
5. Ongoing Maintenance and Improvement
Even after implementation, continuous operation and improvement are required. The accuracy of speech recognition varies depending on the data used and the environment, so regular evaluation and adjustment will ensure that high performance is always maintained.
Speech recognition APIs can be very powerful tools if implemented correctly, but the key to success is preparation before implementation and follow-up after operation. We recommend starting with a small implementation and gradually expanding it while checking the actual effects.
The future of speech recognition APIs
Technological evolution
Speech recognition APIs have evolved rapidly over the past few years, and further technological innovation is expected in the future. In particular, advances in AI and machine learning have significantly improved the accuracy of voice conversion.
Improved accuracy and support for complex voices
Conventional speech recognition can sometimes make mistakes due to noise or speaker habits. However, the latest technology is now able to handle complex speech patterns and changes in emotion. This is due to continuous model updates based on massive amounts of voice data and improved accuracy in feature extraction through deep learning.
Advances in real-time processing
Advances in communications technology have dramatically improved the real-time processing speed of speech recognition APIs. This has enabled smooth connection and processing even in situations where immediacy is required, such as at event venues and live streaming. In the future, speech conversion with even lower latency will become the standard, accelerating the development of interactive applications.
Expanded multilingual support
As globalization progresses, multilingual support for speech recognition APIs is becoming increasingly important. The latest APIs support not only English and Japanese, but many other languages, including those from Asia, the Middle East, and Europe, and allow for flexible switching between languages. This has led to increased use in international service development and multicultural events, leading to market expansion .
Speech recognition API technology will continue to evolve through repeated development and changes. Companies and developers can provide more advanced services by proactively adopting the latest technologies.
New market potential
Speech recognition technology has rapidly evolved alongside advances in AI, and is now widely used in areas such as customer service and meeting minutes. However, the potential of speech recognition APIs does not end there. We will explore the future prospects by proposing applications in new industries and situations that have not received much attention until now.
1. Possibility of hands-free reporting in construction and field work
In the construction industry, there is a growing need for hands-free reporting and recording while working on-site. By utilizing voice recognition APIs, workers can simply verbally report into their smart devices and record in real time. Especially on large-scale projects, accurate information sharing is directly linked to safety and efficiency.
2. New uses of information gathering in disaster response and emergency support
In the chaotic situations of disasters, rapid information gathering and sharing is essential. Using a speech recognition API, testimonies from on-site staff and victims can be instantly converted into text, allowing for analysis and sharing. A multilingual API can also be used in languages other than Japanese, making it useful for providing support to foreign disaster victims.
3. Recording work and sharing knowledge in the agricultural field
Agriculture is one of the industries that has been slow to digitalize, but the introduction of voice recognition APIs is expected to bring about major changes. Farmers can record their work using voice, which can then be later compiled into a database for analysis and sharing of know-how. With an aging agricultural workforce, voice input, which can be easily operated, is a technology with great potential.
4. Personalized tourism and cultural experiences
By incorporating a voice recognition API into guide services at tourist destinations, visitors' questions and responses can be analyzed in real time, enabling more personalized guidance. Furthermore, analyzing voice data can help understand tourists' interest trends and satisfaction levels, which can be used in regional tourism strategies. This is an area that can also lead to the creation of new businesses.
5. Remote medical support in remote islands and depopulated areas
Telemedicine plays an important role in areas where there are no doctors on-site. By utilizing a voice recognition API, patients' explanations of their symptoms can be accurately recorded, facilitating smooth communication with doctors. Accumulating voice data opens up new possibilities for contributing to improving the quality of regional medical care.
6. Developers create innovative services
Speech recognition APIs are powerful tools that enable developers to build new applications and services, reaching new markets such as voice diary apps, voice-based search engines, and assistive tools for people with disabilities. The flexibility of APIs allows them to meet diverse needs across industries.
Recommended voice recognition services
Onkyo SPEECH
Onkyo SPEECH is a cloud-based service that uses Onkyo's proprietary, highly accurate speech recognition engine to transcribe speech . The main features are as follows:
Features
Highly accurate voice conversion
The acoustic model utilizes deep learning to achieve a recognition rate of over 84% even for speech from elderly people whose pronunciation changes.
Automatic language model updates
It learns from misrecognized text and continuously improves accuracy, and can handle industry-specific terminology and dialects.
Resistant to microphone environments
It demonstrates stable recognition performance even in noisy environments and can be connected to a variety of microphone devices.
Supports both cloud and on-premise systems
Depending on the application, you can choose between the batch processing version and the streaming version. Installation in a cloud environment is also smooth.
Improving transcription efficiency
Automatically visualize the contents of meetings and sales calls, improving the quality of meeting minutes and customer service.
Free trial version available
We provide a web app that allows you to test the functionality using 2ch audio files. Ideal for testing before implementation.
As such, Onkyo SPEECH is a voice recognition service that can be used in a wide range of fields, including business, education, and medicine. It is an especially recommended option for those looking for highly accurate recognition performance specialized for Japanese speech .
For more information, please visit the official website: Onkyo SPEECH official page
Summary and future prospects
The importance of speech recognition APIs
Speech recognition APIs are becoming an important technology infrastructure in many industries. Advances in AI and machine learning have dramatically improved the accuracy of voice data recognition, making it possible to handle complex speech and specialized terminology.
In particular, in areas such as customer support and voice assistants, real-time responses are now possible, providing users with a smoother and more efficient experience. Businesses can also provide more reliable services through the automation of tasks and the visualization of information.
Furthermore, the speech recognition API is active in the global market thanks to its multilingual support and translation functionality. By supporting not only Japanese but also English and other languages, it plays a role in lowering the communication barrier in multilingual environments.
At the same time, security and privacy protection are also important points. Voice data often contains personal information, so proper management and operation are required. When implementing this system, it is essential to carefully check the terms of use and data protection policies.
In the future, speech recognition APIs are expected to be used in an even wider range of fields as they are integrated with more advanced processing such as text generation and sentiment analysis. This technology will likely attract more attention as it contributes to the creation of new value in a variety of areas, including education, medicine, welfare, and business.
Start by taking advantage of the free trial and see how it can be used in your business.

