The Measurement of Ultrasonic Hearing

Abstract

Measures of sensory acuity are obtained for varied reasons. For instance, an investigator may wish to know the effects of a drug, or a lesion, on the capacity of an animal to see, hear, or feel stimulation to which it is normally sensitive. More specifically, it is desirable to accurately assess the degree of sensory impairment resulting from some experimental treatment. Depending on the accuracy desired, the experimenter may choose an appropriate measurement technique from among a variety of procedures. No matter which technique is selected, however, the animal is always required to indicate it has detected a stimulus input by responding in some distinctive manner. Typically a cat may learn to move from one end of a box to the other when it hears a tone. Since past experience in the experimental chamber has shown the cat that failure to move during tone presentation resulted in painful electric shock, the cat usually learns to avoid shock by quickly moving across the box. Movement across the box during tone presentation is thus taken to indicate hearing. The tone may then be made progressively weaker until a signal level is reached to which the cat cannot respond, i.e., its threshold of hearing has been reached.