GSM to SNDT Converter

Move GSM telephony speech into MS-DOS SNDT audio online

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DOS Audio Conversion

Place GSM telephony speech into the SNDT format — an MS-DOS sound tool type used in retro computing and historical audio projects.

Server-Side Work

No vintage audio tools needed on your system. The GSM to SNDT conversion runs on our cloud infrastructure through your browser.

Secure and Private

GSM uploads are purged after conversion. SNDT outputs are automatically deleted from servers within 24 hours.

How to convert GSM to SNDT

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose sndt or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your sndt file right afterwards

About formats

GSM 06.10 (Full Rate) is the foundational speech codec of the Global System for Mobile Communications standard, ratified by ETSI in 1991 and deployed across hundreds of cellular networks worldwide. Operating at a fixed 13 kbit/s, the algorithm applies Regular Pulse Excitation with Long-Term Prediction (RPE-LTP) to compress 20 ms frames of 8 kHz mono speech into just 33 bytes each. This approach models the vocal tract as a linear predictive filter, encodes the excitation signal, and leverages pitch periodicity for further reduction — tuned to deliver intelligible voice under the bandwidth constraints of early digital mobile channels. The codec powers not only GSM telephony but also many VoIP applications, voicemail systems, and IVR platforms that benefit from its low bitrate. Three concrete advantages stand out. First, extraordinary compression: one minute of speech fits in roughly 100 KB, enabling efficient storage and transmission. Second, universal tooling — libraries such as libgsm and SoX handle encoding and decoding on every major platform. Third, a royalty-free patent landscape that has encouraged adoption across open-source telephony projects like Asterisk and FreeSWITCH.
Initial release: 1991
SNDT is the audio format associated with Sndtool, an early MS-DOS sound utility from the early 1990s that appeared alongside the spread of Sound Blaster cards in PCs. Unlike the headerless Sounder format, SNDT files include a brief header with the sample rate and data length — a meaningful improvement that let playback software determine timing automatically. Audio data is stored as 8-bit unsigned PCM, typically at 8000 to 22050 Hz in mono. Sndtool functioned as a simple waveform recorder and player, often distributed as shareware or bundled with sound card drivers. A key advantage over competing DOS audio formats was this self-describing header, which eliminated the guesswork of playing unfamiliar files — a real problem before standardized multimedia frameworks existed. The format was also efficient to decode, requiring no decompression and minimal CPU overhead on the 286 and 386 processors of the time. SNDT files served as building blocks for early PC games and multimedia presentations, where developers needed reliable audio across the limited Sound Blaster hardware ecosystem. Today, SNDT survives in retro software archives and is supported by SoX for conversion to modern formats.
Developer: Sndtool (MS-DOS)
Initial release: 1992

Frequently Asked Questions

What is the SNDT format?

SNDT is an early 1990s MS-DOS sound tool format used for storing basic audio samples on vintage personal computers.

Why convert GSM to SNDT?

SNDT is needed for specific DOS-era software and retro computing scenarios where period-correct audio formats are required.

How do I play SNDT files?

SoX and DOSBox can handle SNDT audio. Dedicated vintage audio tools from the DOS era also support native playback.

Is SNDT a high-quality format?

No. SNDT is a simple 8-bit format with modest capabilities. It faithfully stores the decoded GSM signal within its technical limits.

Are my files secure during conversion?

Uploaded GSM files are deleted immediately. SNDT results are removed from our servers within 24 hours for your privacy.