Threshold of hearing

Threshold of Hearing

The threshold of hearing is the minimum sound level of a pure tone that an average ear with normal hearing can hear with no other sound present. It varies across different frequencies and is a key concept in the field of audiology, the science of hearing. The threshold of hearing is typically measured in decibels (dB), a unit that expresses the intensity of a sound.

Definition

The threshold of hearing is defined as 0 dB, but this does not mean the absence of sound. Instead, it represents the faintest sound that the young, healthy ear can detect. The actual threshold can vary significantly among individuals and is influenced by both environmental and physiological factors. For example, age, ear diseases, and prolonged exposure to loud noises can elevate the threshold, leading to hearing impairments.

Measurement

The measurement of the threshold of hearing is conducted using an audiometer, a device that can produce pure tones at various frequencies and intensities. During an audiometric test, the subject is exposed to these tones in a controlled environment, typically a soundproof room. The audiologist gradually decreases the intensity of the tone until the subject can no longer hear it, marking the threshold of hearing for that frequency.

Frequency and Age Effects

The human ear does not hear all frequencies equally. It is most sensitive to frequencies between 2,000 and 5,000 Hz, where the threshold of hearing is lowest. Sensitivity decreases for lower and higher frequencies. Additionally, the threshold of hearing tends to increase with age, a condition known as presbycusis. This age-related hearing loss primarily affects higher frequencies.

Applications

Understanding the threshold of hearing is crucial in various fields. In audiology, it helps in diagnosing hearing loss and in the fitting of hearing aids. In acoustics, it guides the design of soundproofing materials and the development of noise control strategies. Moreover, knowledge of the threshold of hearing is essential in setting occupational safety standards to prevent noise-induced hearing loss.

See Also

• Audiogram
• Hearing loss
• Psychoacoustics
• Sound level meter