SLN to SOU Converter

Export Asterisk SLN recordings to SOU sound file format

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Vintage Audio Format

Move Asterisk SLN telephony audio into the SOU format for legacy audio system compatibility and preservation.

Cloud Processing

No vintage audio software needed. The SLN to SOU conversion runs entirely on our cloud servers.

Private Handling

Your telephony recordings remain confidential. Source and output files are automatically deleted after use.

How to convert SLN to SOU

1

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

2

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

3

Let the file convert and you can download your sou 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
SOU is a raw audio format designation that functions as an alias for unsigned 8-bit PCM data (u8) in the SoX audio processing framework. Files with the .sou extension contain headerless, uncompressed audio samples stored as unsigned 8-bit integers — each byte represents a single amplitude value from 0 to 255, with 128 as the silence midpoint. Because there is no header, playback parameters such as sample rate and channel count must be specified externally. The default assumption is typically mono at 8000 Hz, though the data can represent any rate the recording hardware supported. The u8 encoding that SOU aliases is one of the simplest possible digital audio representations, predating structured audio containers like WAV and AIFF. Raw unsigned PCM was commonly produced by early sound cards and digitizers in the late 1980s and early 1990s, when storage constraints and limited processing power made headerless formats a practical choice. One advantage is absolute simplicity: SOU files can be read by any program capable of basic file I/O, with no parsing of container structures or metadata decoding required — useful for embedded systems, hardware diagnostics, and educational contexts where audio fundamentals are being explored. The format's minimal overhead also means that conversion to any modern container is lossless and instantaneous, since the raw PCM samples can be wrapped in a WAV or AIFF header without any transcoding.
Developer: SoX Contributors
Initial release: 1991

Frequently Asked Questions

Why convert SLN to SOU?

SOU is a legacy sound format required by certain vintage audio systems. Converting SLN to SOU enables playback in those environments.

What opens SOU files?

SoX and specific legacy audio tools can process SOU format sound files.

Is SOU still in use?

SOU is primarily a legacy format. Modern use is limited to retrocomputing, preservation, and specific legacy system requirements.

Can I batch convert files?

Upload multiple SLN recordings at once and convert them all to SOU in a single efficient session.

How is data privacy maintained?

SLN uploads are deleted after conversion, and SOU outputs are purged from our servers within 24 hours.