# Audio networking using commodity hardware

*2004-10-01 — idea*


Many everyday electronic devices such as laptops, PDAs and telephones are
able to play and record audio. Invariably this ability is used to interface
with people, playing or recording music, speech or sound effects. However,
it is just as possible for the devices to communicate with each other,
exchanging data encoded into sounds. This project aims to allow computers,
separated by short distances within a room to communicate by transmitting
sounds between them.

In certain ways, audio based data communication already occurs. The prime
example, the modem, encodes digital data into sounds suitable for
transmission over a telephone line. Similarly, telephones communicate with
exchanges using tones to encode telephone numbers. Historically, old
computers would sometimes store data on standard audio cassettes.

The techniques used in modems will likely be a useful point of reference;
however the challenges of sending audio reliably across a room are a little
different. Telephone lines have fairly well known bandwidths and noise
characteristics, whereas rooms vary greatly in their acoustics and hence the
distortions they apply to sound. Additionally, the variety of noise that
must be dealt with will be larger, since people and machinery may also be
present. Therefore different encoding schemes may be needed.

Audio networking has some important differences when compared with other
wireless networking technologies. Radio based systems such as 802.11 and to
some extent Bluetooth will radiate throughout a building, permeating walls
and floors. Because buildings are usually architected with soundproofing in
mind, audio signals are much better confined to a particular room. Ignoring
glass windows, such confinement is also applicable to infrared signals.
However, line of sight is normally needed for infrared, whilst sound can be
more omnidirectional.

The most obvious difference to a user of audio networking will be that they
are able to perceive it themselves - assuming that the audible frequency
range and not ultrasound is used. Since noise is objectionable to humans,
causing headaches, irritation and lowering productivity, it would be
imprudent to use audio for continuous data transmission. Short bursts of
communication however should not be too distracting, particularly if
initiated at the user's request.

Since audio networking will have a much lower capacity than existing
systems, the most effective use will exploit its architecturally limited
range and human awareness. Such a use could be a system for portable
computers to discover their location within a building. If there were a
fixed computer in a room which knew its location, then portable systems
could configure themselves by sending an audible signal and receiving a
reply from the fixed station. Such a system could for example be used to
obtain information on the nearest printer or the configuration for the
room's 802.11 wireless network.

See also [Context-Aware Computing with Sound](https://anil.recoil.org/papers/audio-networking) for more background.
Status: Completed
Level: PartII
Year: 2004
Project: Ubiquitous Interaction Devices
Supervisors: Anil Madhavapeddy
Students: Gareth P. Williams

## Related

- [Context-Aware Computing with Sound](https://anil.recoil.org/papers/audio-networking) (paper, 2003-10-01)

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Canonical: https://anil.recoil.org/ideas/commodity-audio-networking
Type: idea
Tags: audio, networking, ubicomp