Compared to NOISE, which is unwanted sound, a SIGNAL is any sound or message which is meant to be listened to, measured or stored.

In SOUNDSCAPE studies, sound signals are always treated in relation to their AMBIENT or KEYNOTE context, since they complement that context in the same way figure and ground are related in visual perception. Thus, a study of signals also reveals important information about the overall sound environment. The increase in the level of emergency warning signals during this century, for instance, has been closely proportional to the increase in the AMBIENT NOISE LEVEL of cities.

Compare: AUDIO, MESSAGE, SIGNAL-TO-NOISE RATIO, SOUND EFFECT, SOUND EVENT, SOUND OBJECT.

Sound signals may be studied in any of the following ways:

• on the basis of their acoustic characteristics, which may represent a recognized code or other pattern pertaining to their use (see TYPOLOGY);
• subjectively, by their individually perceived meanings;
• historically, according to their evolution within a given social context (see MORPHOLOGY);
• comparatively, by type and function in different cultures or periods;
• symbolically, according to their connotative and associative meanings.

Sound signals are important in the way in which they regulate the life of a community and reflect its character. Those of historic importance may be termed SOUNDMARKs. The area over which a sound signal may be heard is its profile or ACOUSTIC SPACE, which may be regarded as its sphere of influence. In modern urban environments, many community signals are disappearing both physically and acoustically with rising ambient noise levels.

See also: ACOUSTIC HORIZON, DISAPPEARING SOUND, SOUND PHOBIA, SOUND ROMANCE.

Sound Example: B.C. Ferry horns, Horseshoe Bay, West Vancouver, B.C.

Sound Example: Steam whistle, Vancouver harbour.

Sound Example: Diaphone type foghorn, Ft. Amherst, St. John's, Newfoundland.

Sound Example: Noon siren, Alliance, Alberta.

Sound Example: Cathedral bell, Salzburg, Austria.