Noise music is a category of music that is characterised by the expressive use of noise within a musical context. This type of music tends to challenge the distinction that is made in conventional musical practices between musical and non-musical sound. Noise music includes a wide range of musical styles and sound-based creative practices that feature noise as a primary aspect. It can feature acoustically or electronically generated noise, and both traditional and unconventional musical instruments. It may incorporate live machine sounds, non-musical vocal techniques, physically manipulated audio media, processed sound recordings, field recording, computer-generated noise, stochastic process, and other randomly produced electronic signals such as distortion, feedback, static, hiss and hum.