Which type of sonar does not transmit sound?

Passive sonar is a type of sonar system that does not transmit sound. Instead, it listens for sounds made by other objects, such as submarines or marine life, in the water. This ability to detect sounds without emitting any signals gives passive sonar the advantage of operating without revealing its location, making it an ideal choice for reconnaissance and stealth operations.

In contrast, active sonar emits sound waves and then listens for the echoes that bounce back, allowing the user to determine the distance and characteristics of objects underwater. Ultrasound is a term typically associated with sound waves above the hearing range of humans and is commonly used in medical imaging, but it technically falls under the broader category of sound transmission. Plotting as a term generally refers to the method of representing data or sounds visually, rather than being a type of sonar itself.