SLN to SNDT Converter

Transform Asterisk SLN recordings into MS-DOS SNDT audio

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Legacy DOS Audio

Bridge Asterisk telephony and vintage computing — convert SLN recordings into the MS-DOS SNDT format.

Cloud Processing

No DOS emulator or vintage sound card needed. The SLN to SNDT conversion runs entirely on our cloud servers.

Data Protection

PBX recordings remain confidential. Source files are erased post-conversion, outputs purged within 24 hours.

How to convert SLN 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

SLN (Signed Linear) is a headerless raw audio format storing 16-bit signed linear PCM samples at 8000 Hz mono, most closely associated with Asterisk — the open-source PBX framework developed by Digium (now Sangoma Technologies). Within Asterisk, SLN serves as the native internal audio representation: every codec transcoding operation passes through signed linear as an intermediate step. This makes SLN the backbone of Asterisk's codec translation architecture. The format contains nothing but raw samples — no headers, no metadata, no framing — so parameters must be known in advance. While this lack of self-description might seem limiting, it is actually an advantage in telephony where sample format is fixed by convention and every overhead byte matters across thousands of simultaneous channels. The 8000 Hz rate aligns with the G.711 standard for traditional telephony, capturing the full 300-3400 Hz voice band. Asterisk also supports extended variants (sln16, sln32, sln48) for wideband audio. SLN files require no decoding — just direct memory mapping — making them ideal for real-time mixing, conferencing, and prompt playback in high-density VoIP environments.
Initial release: 1999
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

Why convert SLN to SNDT?

SNDT is a DOS-era sound variant required by certain legacy systems. Converting SLN to SNDT makes telephony audio usable in those environments.

What handles SNDT files?

SoX, certain DOS audio tools, and retro computing utilities can read and process SNDT files.

How is SNDT different from SND?

SNDT is a specific MS-DOS variant of the SND family. It uses a simpler structure suited to early PC sound hardware capabilities.

Can I convert multiple SLN recordings?

Upload several SLN files at once and convert them all to SNDT in a single batch — fast and efficient.

Is the process confidential?

Your SLN files are deleted after conversion, and SNDT outputs are removed from our servers within 24 hours.