When a projector sends out a sound, the signal spreads away from the source (see Sound Spreading). If the projector is omnidirectional, the sound will spread out equally in all directions. However, if the projector is directional, the sound will be stronger in some directions than in others. Fish finders and echosounders are typically designed to create a cone shaped signal, with the point at the transducer. The angle of this cone determines the coverage area of the signal. Directional projectors come with a variety of narrow and wide cone angles.
Highly directional sources must be large in size compared to the wavelength of the sound being transmitted. In some cases a single, large projector is used, particularly for high frequency signals, but at lower frequencies this is often not feasible. It is then more convenient to use an array of smaller projectors that transmit in unison to construct a directional projector.
- How is sound used to locate fish?
- How is sound used to measure water depth?
- How is sound used to navigate underwater?