Pure-Tone Testing

Types of Tests:

A pure-tone air conduction hearing test determines the faintest tones a person can hear at selected pitches (frequencies), from low to high. During this test, earphones are worn so that information can be obtained for each ear.

Sometimes, use of earphones for the test is not possible, such as when a child refuses to wear them. In these cases, sounds are presented through speakers inside a sound booth (called sound-field screening). Since sound-field screening does not give ear-specific information, a unilateral hearing loss (hearing loss in only one ear) may be missed.

The person taking the test may be asked to respond to the sounds in a variety of ways, such as by:

• Raising a finger or hand
• Pressing a button, pointing to the ear where the sound was received
• Saying "yes" to indicate that the sound was heard

The results are recorded in an audiogram.

Sometimes, young children are given a more play-like activity to indicate response. The most common techniques involve visual reinforcement audiometry (VRA) and conditioned play audiometry (CPA).

Visual reinforcement audiometry is the method of choice for screening children between 6 months and 2 years of age. The child is trained to look toward a sound source. When the child gives a correct response (e.g., looking to a source of sound when it is presented), the child is "rewarded" through a visual reinforcement. Example rewards include getting to watch a toy that moves or a flashing light.

Conditioned play audiometry can be used as the child matures and is commonly used with toddlers and preschoolers (ages 2–5). The child is trained to perform an activity each time a sound is heard. The activity may involve putting a block in a box, placing pegs in a hole, or putting a ring on a cone.

If there is a blockage, such as wax or fluid, in the outer or middle ears, a method called pure- tone bone conduction testing may be used. With this technique, the blockage is bypassed by sending a tone through a small vibrator placed behind the ear (or on the forehead). The signal reaches the inner ear (or cochlea) directly through gentle vibrations of the skull. This testing can measure response of the inner ear to sound independently of the outer and middle ears. In these cases, this test helps the audiologist determine the type of hearing loss being measured.