This short text deals with noise machines as art objects and introduces some artists working with this technique.
In the course of the past three decades the locution “sound art” emerged as a new framework to describe an art form where sound is used as main material of the artwork.
Bernd Schulz describes sound art as a discipline on the frontier between the visual arts and music, situated in the context of an expanded concept of sculpture .
The use of the term “sound” rather than “music” underlines the inclusion of noise as valuable acustic perception. “In the context of music, sounds are regarded as messengers of subjective inner worlds; noises, on the other hand, are conceived of a symbols indicating trivial occurrences or objects of everyday life”. 
In the historical path to the acceptation of noise as an artistic medium, one of the most relevant contributors is the composer Pierre Schaeffer. In the 1940s, with the appearance of the first tape recording machines, rather than using them for their common documentary use (music, nature sounds, environmental sounds), he worked on isolating, fragmenting and decontextualizing noises from daily life objects. He also worked with spazialized sounds, hence redefining the space through sound in a sculptural way.
Differently from other forms of musical consumption like the concert, in sound sculptures or installations the sounds have “no defined beginning or previously determinate end” .
To achieve this effect, sound may be reproduced through speakers, actuators or similar devices, but also materially generated through mechanical or robotic movement. The sound of common object is often mechanized by the use of motors or other robotic devices.
The materiality of the object is often used as a stochastic generator: John Cage was one of the first talking about the concept of indeterminacy in musical composition, and used aleatory sounds produced by objects such as tin cans.
Already in the 50s, the sculptor Jean Tinguely worked on chance-driven mechanical sound machines:
“Tinguely’s fantasy machines with pre-programmed elements of chance, the so-called ‘Métamatics’, are quite spectacular. They are machines producing drawings, or self-destructive machines. His welded iron constructions represent ironic attacks on the purpose of the era of technology.” 
The Greek artist Vassilakis Takis creates mechanical sound sculptures using magnetism as chance generator:
“The Greek artist Takis first began exhibiting musical sculptures like the one seen here [Musical Hannover, 1974] in 1965. Concerned with the repetition of sound, these sculptures use magnetic waves caused by electricity to activate the plucking of strings or other sound-making materials. Takis’ sound sculptures seek to implement a natural means of generating sound, separated from the arbitrary decision-making process of a lone artist; by using magnetism, Takis presents sound as a discoverable object, a series of events outside of his control.” 
Prepared motors are some of the devices used by the Swiss-born artists Pe Lang and Zimoun to create their installations, in which sound is generated by the chaotic movement of obsessively repeated modules:
“[…] physical materials are made to generate sound by vibrating them using computer controlled machines and robots. […] these works are created by using small machines comprised of computer-monitored and programmed electromagnetic lifts, electromagnets and vibrating motors, in combination with different kinds of materials.” 
The German artist Josefine Günschel used a similar technique in “Steel bands”:
“Metal strips over two metres in length and made of suspension steel are struck by motorised metal hammers causing them to swing, whip and clash against each other. After a while the vibrations become slower and the metal strips return to their initial positions before being struck once again and sent into motion.
A nervous, pulsating environment is created in which events take on an unusually life-like character. “ 
- Bernd Schulz, “Resonanzen. Aspekte der Klangkunst”, Stiftung Saarländischer Kulturbesitz, 2003