WMA to SLN Converter

Create Asterisk PBX signed linear audio from WMA

Drop files here. 1 GB maximum file size or Sign Up
to
Facebook Amazon Microsoft Tesla Nestle Walmart L'Oreal

Asterisk PBX Ready

SLN is what Asterisk expects — convert WMA for your VoIP phone system.

Bulk Deployment

Process all WMA prompts to SLN simultaneously.

Online Encoding

No Asterisk server needed for conversion — produce SLN from WMA in your browser.

How to convert WMA to SLN

1

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

2

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

3

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

About formats

WMA (Windows Media Audio) is a family of proprietary audio codecs developed by Microsoft and first released in 1999 as part of the Windows Media framework. Created to compete with MP3 and AAC, WMA Standard uses perceptual coding to deliver what Microsoft claimed was near-CD quality at bitrates as low as 64 kbps — roughly half the data rate MP3 typically needed for comparable results. The codec family grew to include WMA Professional for surround sound and high-resolution audio, WMA Lossless for bit-perfect archival compression, and WMA Voice optimized for spoken content at very low bitrates. Deep integration with Windows, Windows Media Player, and the Zune ecosystem gave WMA a strong distribution advantage throughout the 2000s, and digital rights management (DRM) support made it attractive to online music stores of that era. Encoding and decoding are handled natively by Windows, requiring no third-party software for playback on any Windows machine. Cross-platform support has improved through libraries like FFmpeg and GStreamer, though WMA remains less universally compatible than MP3 or AAC on non-Microsoft devices. The format still appears in legacy media libraries, though newer codecs have largely taken its place for streaming and portable use.
Initial release: 1999
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

Frequently Asked Questions

Why convert WMA to SLN?

SLN is the native raw audio format for Asterisk PBX systems. VoIP prompts, hold music, and IVR recordings must be in SLN — Asterisk cannot decode WMA files at all.

Which systems and software can use SLN files?

Asterisk PBX, FreePBX, Issabel, and other VoIP platforms consume SLN for system prompts, on-hold audio, and interactive voice response menus without any extra modules.

What audio specifications does SLN use?

SLN is headerless raw PCM — 8 kHz sample rate, 16-bit signed integer, little-endian byte order. These specs match standard telephony requirements for clear voice reproduction.

Will my WMA audio sound good after converting to SLN?

SLN is telephony-grade at 8 kHz, so the output is voice-optimized rather than music-quality. Speech and announcements convert well; complex audio may lose some detail.

Can I convert multiple WMA prompts to SLN in one go?

Yes — upload your entire collection of WMA voice prompts and convertio.tools produces individual SLN files for each, letting you deploy a complete Asterisk sound library quickly.