How to Leverage Speech-to-Text With Node.js

The purpose of this article is to provide a brief overview of speech recognition technology and its common applications, and to demonstrate a free speech-to-text API which can be used to transcribe audio in MP3 and WAV file formats. This demonstration will include step-by-step instructions to call this API using ready-to-run Node.js code examples.

Overview of Speech Recognition

It’s easy to think of speech recognition as a relatively new addition to the contemporary technology landscape. That’s only a partial truth; speech recognition mechanics have been around for more than half a century, beginning with basic, limited numerical/word recognition systems developed by a few pioneering technology companies during the early 1950s. Despite its long history and proliferation in the world of smart consumer devices over the last decade or so, however, speech recognition still registers as one of the more abstract technologies on the market today.  That’s because all speech recognition services straddle the fields of computer science, computational linguistics, and mathematics/statistics, requiring sizable input from each field to achieve accurate speech-to-text results.  

At an (extremely) high level, for speech recognition services to perform their most rudimentary task, a given audio file must first be pre-processed to optimize its quality. After that, it must be broken down into smaller component signals and sorted. These sorted signals must be small enough so that a mathematical model can match them with certain phonemes (language-specific sounds that come together to create words; think “eeee” or “ahhh” noises), which facilitate a comparison with phrases or sentences in that language. Ultimately, the goal of a speech recognition service is a humble one: to make the most accurate possible guess at which words are being used in an audio recording, and to continuously improve and expand its repertoire of linguistic data until the guesses reach an acceptable level of accuracy.

This complex and inherently limited system of informed guessing makes even the most basic speech recognition services as language and dialect dependent as they are audio-quality dependent.  Variations in language, accent, vocabulary, and the presence of loud background noises create boundaries which are difficult for a single speech-to-text model to overcome. In addition, this complexity reflects the underlying fact that speech recognition services are highly resource intensive, leaning on bulky (and ever-growing) reference datasets to make phonetic comparisons and requiring considerable computing power to leverage those datasets efficiently. These factors collectively make training a brand-new speech-to-text model a difficult task.

Applications of Speech Recognition

It is largely due to a few ubiquitous innovations in the greater technology market — most notably the growth of near-infinite cloud data storage solutions — that speech recognition has become the efficient, useful consumer service we now recognize it as in our everyday lives. We can talk directly to many of our hand-held, home and office devices to automatically query online information we need, to record and organize our own thoughts for later use, to hear text messages read out loud to us, and much more.

Presently, consumer applications are just the tip of the speech recognition iceberg. Advancements in speech recognition’s many interconnected processes have created the opportunity to scale audio transcription output and have encouraged a growing number of commercial applications for speech-to-text conversions as a result.  Examples of this are present all around us. Many virtual meeting platforms now employ speech recognition services (often in real-time) to make transcriptions of team presentations, and the resulting text can be easily stored for anyone who might’ve missed the meeting. Chat bots leverage speech recognition to help guide us through our options on the phone, and transcribed audio recordings from those conversations can be put to another use: informing better customer service practices in the future. Lectures, interviews, speeches, and other oratory events you or a colleague may have attended can be recorded through personal devices and transcribed to eliminate the labor-intensive distraction of manual notetaking.  Those transcriptions can be processed by, for example, Natural Language Processing (NLP) models to seek previously unseen (or unheard) insights from the transcribed text.

It's worth mentioning that practical content moderation and SEO functions are also gained from a scalable speech-to-text analysis service — this time in the context of enterprise data storage. Given the unreliable nature of most client-side content uploads, automatically transcribing audio files uploaded to a website creates an easy opportunity to moderate the parent audio file’s language to ensure it is safe for all listeners (for example: to see if it contains exceedingly controversial language, hate speech, or any other form of harassment towards an individual or group). This considerably reduces the workload of a human content moderator and increases their efficacy.  Those same transcriptions can additionally be used to generate useful keywords, making the audio file more easily searchable and retrievable from a large database.

Demonstration: Cloudmersive Speech-to-Text API

One way to take advantage of speech recognition as a service is through the inclusion of the Cloudmersive speech-to-text API. This API currently supports MP3 or WAV formats and employs a Deep Learning Artificial Intelligence model to provide audio transcriptions with a high degree of accuracy.  The API parameters are very straightforward, requiring only the input audio file and a Cloudmersive API key (the API key can be obtained for free by registering a free account on our website; this account will yield a limit of 800 API calls per month). Below, I will demonstrate how to structure your API call using complementary Node.js code snippets.

The first step is to install the Node.js SDK.  You may do so by running the following command:

npm install cloudmersive-speech-api-client --save

Alternatively, you may add this snippet to your package.json:

  "dependencies": {
    "cloudmersive-speech-client": "^1.1.5"
  }

 With installation complete, you can structure your API call using the following code block. At this point, ensure you have the following parameters ready:

1. Your MP3 or WAV audio file.
2. Your Cloudmersive API Key.

var CloudmersiveSpeechApiClient = require('cloudmersive-speech-api-client');
var defaultClient = CloudmersiveSpeechApiClient.ApiClient.instance;

// Configure API key authorization: Apikey
var Apikey = defaultClient.authentications['Apikey'];
Apikey.apiKey = 'YOUR API KEY';



var apiInstance = new CloudmersiveSpeechApiClient.RecognizeApi();

var speechFile = Buffer.from(fs.readFileSync("C:\\temp\\inputfile").buffer); // File | Speech file to perform the operation on.  Common file formats such as WAV, MP3 are supported.


var callback = function(error, data, response) {
  if (error) {
    console.error(error);
  } else {
    console.log('API called successfully. Returned data: ' + data);
  }
};
apiInstance.recognizeFile(speechFile, callback);

With that, you’re all finished; no further code snippets are required. A successful API call will return a TextResult string containing the API’s transcription results. It’s important to remember that the quality of the audio in your input file will have a significant impact on the API’s ability to create an accurate transcription, so it’s recommended to preprocess and optimize audio quality ahead of this operation as much as possible.