Your audio format might not be supported. Java ME makes no guarantees beyond what's specified in section A.2.2 from Mobile Service Architecture Specification Version 1.1.0b – 18-August-2008 (available by download from JSR-000248 Mobile Service Architecture ).
Audio formats from A.2.2 Content Formats:
1. 8 kHz, 8-bit linear PCM audio in WAV
2. AMR-NB* (AMR-NB support is NOT REQUIRED for compliant development tools, device emulators, or a reference implementation running on a device emulator.)
Also see: javax.microedition.media.Manager ; and methods: .getSupportedContentTypes(), getSupportedProtocols(String content_type) of the Manager class. You can find out from Manager what additional audio formats your specific device supports.