--- name: speech-to-text-basic-response title: Understanding speech recognition results description: Regardless of the interface that you use, the IBM Watson® Speech to Text service returns transcription results that reflect the parameters that you specify. The service returns all JSON response content in the UTF-8 character set. last-updated: 2025-11-25 --- > ## Documentation Index > The table of contents for this documentation set is at https://cloud.ibm.com/docs/speech-to-text?format=markdown > The index for all IBM Cloud docs is at: https://cloud.ibm.com/docs/llms.txt > Use these files to discover more information as needed. # Understanding speech recognition results {: #basic-response} Regardless of the interface that you use, the IBM Watson® Speech to Text service returns transcription results that reflect the parameters that you specify. The service returns all JSON response content in the UTF-8 character set. {: shortdesc} ## Basic transcription response {: #response-content} The service returns the following response for the examples in [Making a speech recognition request](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-basic-request&format=markdown). The examples pass only an audio file and its content type. The audio speaks a single sentence with no noticeable pauses between words. ```json { "result_index": 0, "results": [ { "alternatives": [ { "confidence": 0.96, "transcript": "several tornadoes touch down as a line of severe thunderstorms swept through Colorado on Sunday " } ], "final": true } ] } ``` {: codeblock} The service returns a `SpeechRecognitionResults` object, which is the top-level response object. For these simple requests, the object includes one `results` field and and one `result_index` field: - The `results` field provides an array of information about the transcription results. For this example, the `alternatives` field includes the `transcript` and the service's `confidence` in the results. The `final` field has a value of `true` to indicate that these results will not change. - The `result_index` field provides a unique identifier for the results. The example shows final results for a request with a single audio file that has no pauses, and the request includes no additional parameters. So the service returns a single `result_index` field with a value of `0`, which is always the initial index. If the input audio is more complex or the request includes additional parameters, the results can contain much more information. ### The alternatives field {: #response-alternatives} The `alternatives` field provides an array of transcription results. For this request, the array includes just one element. - The `transcript` field provides the results of the transcription. - The `confidence` field is a score that indicates the service's confidence in the transcript, which for this example exceeds 90 percent. The `final` and `result_index` fields qualify the meaning of these fields. Internal changes and improvements to the service can affect transcripts and confidence scores. For example, speech recognition may be improved to return more precise transcription results. Similarly, transcript and word confidence scores might change slightly as a result of improved speech recognition. Such changes are expected to be modest, but do not expect transcripts and confidence scores to remain unchanged over time. {: important} ### The final field {: #response-final} The `final` field indicates whether the transcript shows final transcription results: - The field is `true` for final results, which are guaranteed not to change. The service sends no further updates for final results. - The field is `false` for interim results, which are subject to change. If you use the `interim_results` parameter with the WebSocket interface, the service returns evolving hypotheses in the form of multiple `results` fields as it transcribes the audio. For interim results, the `final` field is always `false` and the `confidence` field is always omitted. For more information about using the WebSocket interface to obtain interim results with large speech models, previous- and next-generation models, see the following topics: - [Interim results](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-interim&format=markdown#interim-results) - [How the service sends recognition results](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-websockets&format=markdown#ws-results) ### The result_index field {: #response-result-index} The `result_index` field provides an identifier for the results that is unique for that request. If you request interim results, the service sends multiple `results` fields for evolving hypotheses of the input audio. The indexes for interim results for the same audio always have the same value, as do the final results for the same audio. The same index can also be used for multiple final results of a single request. Regardless of whether you request interim results, the service can return multiple final results with the same index if your audio includes pauses or extended periods of silence. For more information, see [Pauses and silence](#response-pauses-silence). Once you receive final results for any audio, the service sends no further results with that index for the remainder of the request. The index for any further results is incremented by one. If your audio produces multiple final results, concatenate the `transcript` elements of the final results to assemble the complete transcription of the audio. Assemble the results in the order in which you receive them. When you assemble a complete final transcript, you can ignore interim results for which the `final` field is `false`. ### Additional response content {: #response-additional-parameters} Many speech recognition parameters impact the contents of the service's response. Some parameters can cause the service to return multiple transcription results: - `end_of_phrase_silence_time` - `interim_results` - `split_transcript_at_phrase_end` Some parameters can modify the contents of a transcript: - `profanity_filter` - `redaction` - `smart_formatting` Other parameters can add more information to the results: - `audio_metrics` - `keywords` and `keywords_threshold` - `max_alternatives` - `processing_metrics` and `processing_metrics_interval` - `speaker_labels` - `timestamps` - `word_alternatives_threshold` - `word_confidence` For more information about the available parameters, see [Using speech recognition parameters](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-service-features&format=markdown#features-parameters) and the [Parameter summary](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-summary&format=markdown). ## Pauses and silence {: #response-pauses-silence} How the service returns results depends on the interface and the model that you use for speech recognition, as well as the audio that you pass to the service. By default, the service transcribes an entire audio stream as a single utterance and returns a single final result for all of the audio. However, the service can return multiple final results in response to the following conditions: - The audio contains a pause or extended silence between spoken words or phrases. For most languages, the default pause interval that the service uses to determine separate final results is 0.8 seconds. For Chinese, the default interval is 0.6 seconds. You can use the `end_of_phrase_silence_time` parameter to change the duration of the pause interval. For more information, see [End of phrase silence time](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-parsing&format=markdown#silence-time). - *For previous-generation models,* the utterance reaches a two-minute maximum. The service splits a transcript into multiple final results after two minutes of continuous processing. The following examples show responses with two final results from the HTTP and WebSocket interfaces. The same input audio is used in both cases. The audio speaks the phrase "one two three four five six," with a one-second pause between the words "three" and "four." The examples use the default pause interval for speech recognition. - *For the HTTP interfaces,* the service always sends a single `SpeechRecognitionResults` object. The `alternatives` array has a separate element for each final result. The response has a single `result_index` field with a value of `0`. ```json { "result_index": 0, "results": [ { "alternatives": [ { "confidence": 0.99, "transcript": "one two three " } ], "final": true }, { "alternatives": [ { "confidence": 0.99, "transcript": "four five six " } ], "final": true } ] } ``` {: codeblock} - *For the WebSocket interface,* the service sends the same results as the previous example. The response includes a single `SpeechRecognitionResults` object, the `alternatives` array has a separate element for each final result, and the response has a single `result_index` field with a value of `0`. ```json { "result_index": 0, "results": [ { "alternatives": [ { "confidence": 0.99, "transcript": "one two three " } ], "final": true }, { "alternatives": [ { "confidence": 0.99, "transcript": "four five six " } ], "final": true } ] } ``` {: codeblock} With the WebSocket interface, responses for interim results contain more JSON objects. For more information about using the WebSocket interface to obtain interim results with large speech models, previous- and next-generation models, see the following topics: - [Interim results](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-interim&format=markdown#interim-results) - [How the service sends recognition results](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-websockets&format=markdown#ws-results) Silence of 30 seconds in streamed audio can result in an inactivity timeout. For more information, see [Timeouts](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-input&format=markdown#timeouts). {: note} ## Speech hesitations and hesitation markers {: #response-hesitation} Speech often includes hesitations or verbal pauses, which are also referred to as disfluencies. Hesitations occur when the user inserts fillers such as "uhm", "uh", "hmm", and related non-lexical utterances while speaking. The service handles hesitations differently for large speech models, previous- and next-generation models. ### Hesitations for previous-generation models {: #response-hesitation-prev} For previous-generation models, the service includes hesitation markers in transcription results for most languages. Different languages can use different hesitation markers or not indicate hesitations at all: - *For US English,* hesitation markers are indicated by the token `%HESITATION`. Words that generate hesitation markers are `aah`, `ah`, `hm`, `hmm`, `huh`, `huh-uh`, `hum`, `ohh`, `ugh`, `uh`, `uh-huh`, `uh-oh`, `uh-uh`, `um`, and `um-hum`. - *For Japanese,* hesitation markers typically begin with `D_`. - *For Spanish,* the service does not produce hesitation markers. The following example shows the token `%HESITATION` for a US English transcript: ```json { "result_index": 0, "results": [ { "alternatives": [ { "confidence": 0.99, "transcript": ". . . that %HESITATION that's a . . ." } ], "final": true } ] } ``` {: codeblock} Hesitation markers can appear in both interim and final results. Enabling smart formatting prevents hesitation markers from appearing in final results for US English. For more information, see [Smart formatting](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-formatting&format=markdown#smart-formatting). Hesitation markers can also appear in other fields of a transcript. For example, if you request [Word timestamps](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-metadata&format=markdown#word-timestamps) for the individual words of a transcript, the service reports the start and end time of each hesitation marker. ```json { "result_index": 0, "results": [ { "alternatives": [ { "timestamps": [ . . . [ "that", 7.31, 7.69 ], [ "%HESITATION", 7.69, 7.98 ], [ "that's", 7.98, 8.41 ], [ "a", 8.41, 8.48 ], . . . ], "confidence": 0.99, "transcript": ". . . that %HESITATION that's a . . ." } ], "final": true } ] } ``` {: codeblock} Unless you need to use them for your application, you can safely filter hesitation markers from a transcript. {: note} ### Hesitations for next-generation models {: #response-hesitation-next} For next-generation models, the service includes the actual hesitations words in all transcription results. Next-generation models treat hesitations as words, so hesitations can appear in interim results, final results, and other fields such as the results for word timestamps. Next-generation models do not produce hesitation markers, and enabling smart formatting does not cause hesitations to be removed from final results. Different languages can identify different hesitation words: - *For US English,* common hesitation words, as for previous-generation models, are `aah`, `ah`, `hm`, `hmm`, `huh`, `huh-uh`, `hum`, `ohh`, `ugh`, `uh`, `uh-huh`, `uh-oh`, `uh-uh`, `um`, and `um-hum`. Not all of these hesitation words might appear in transcripts. - *For Japanese,* hesitation words typically consist of half-width characters such as `ｱ`, `ｱﾉｰ`, `ｳｰﾝ`, `ｴｰﾄ`, `ﾏ`, `ﾃ`, `ﾏ`, and `ﾝｰﾄ`. Some hesitations might be recognized as full-width characters. To increase the likelihood of seeing hesitations in your response, you can use a custom language model. In the custom model, add corpora that include the hesitations or create custom words whose sounds-likes capture the way users say the disfluencies. For more information about custom language models, see [Creating a custom language model](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-languageCreate&format=markdown). The following example shows the hesitation "uhm" in a US English transcript: ```json { "result_index": 0, "results": [ { "alternatives": [ { "confidence": 0.99, "transcript": ". . . that uhm that's a . . ." } ], "final": true } ] } ``` {: codeblock} ## Capitalization {: #response-capitalization} For most languages, the service does not use capitalization in response transcripts. If capitalization is important for your application, you must capitalize the first word of each sentence and any other terms for which capitalization is appropriate. The service applies automatic capitalization only to the following languages and models. The service always applies this capitalization, regardless of whether you use smart formatting. - *For US English previous-generation models,* the service capitalizes many proper nouns. For example, the service returns the following transcript for the phrase *barack obama graduated from columbia university*: ```text Barack Obama graduated from Columbia University ``` {: codeblock} The service does not capitalize proper nouns for US English with next-generation models. - *For German next-generation models,* the service capitalizes many nouns. For example, the service returns the following transcript for the phrase *er braucht erst einen neuen eintrag ins vokabular punkt*: ```text er braucht erst einen neuen Eintrag ins Vokabular Punkt ``` {: codeblock} The service does not capitalize nouns for German with previous-generation models. ## Punctuation {: #response-punctuation} The service does not insert punctuation in response transcripts by default. You must add any punctuation that you need to the service's results. For some languages, you can use smart formatting to direct the service to substitute punctuation symbols, such as commas, periods, question marks, and exclamation points, for certain keyword strings. For more information, see [Smart formatting](https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-formatting&format=markdown#smart-formatting).