echo: To bounce back. For example, sound bouncing off walls of a tunnel, and returning to their source. Radio waves emitted above the surface can also bounce off the bedrock underneath an ice sheet — then return to the surface. Or ideas or events that seem to reflect one or more others, as a reverberating sound might.
echolocation: (in animals) A behavior in which animals emit calls and then listen to the echoes that bounce back off of solid things in the environment. This behavior can be used to navigate and to find food or mates. It is the biological analog of the sonar used by submarines.
fetus: (Adj. fetal ) The term for a mammal or other large animal during its later-stages of development in the womb. For humans, this term is usually applied after the eighth week of development.
hertz: The frequency with which something (such as a wavelength) occurs, measured in the number of times the cycle repeats during each second of time.
navigate: To find one’s way through a landscape using visual cues, sensory information (like scents), magnetic information (like an internal compass) or other techniques.
sonar: A system for the detection of objects and for measuring the depth of water. It works by emitting sound pulses and measuring how long it takes the echoes to return.
sound wave: A wave that transmits sound. Sound waves have alternating swaths of high and low pressure.
technology: The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.
tissue: Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
tumor: A mass of cells characterized by atypical and often uncontrolled growth. Benign tumors will not spread; they just grow and cause problems if they press against or tighten around healthy tissue. Malignant tumors will ultimately shed cells that can seed the body with new tumors. Malignant tumors are also known as cancers.
ultrasound: (adj. ultrasonic) Sounds at frequencies above the range that can be detected by the human ear. Also the name given to a medical procedure that uses ultrasound to “see” within the body.
wave: A disturbance or variation that travels through space and matter in a regular, oscillating fashion.
whale: A common, but fairly imprecise, term for a class of large mammals that lives in the ocean. This group includes dolphins and porpoises.