Frequency

Frequency Overview

Frequency is how fast a sound wave vibrates, measured in Hertz (Hz). Lower frequencies under 500Hz are low pitch tones that bend around objects more easily. Higher frequencies up to 8000Hz are high pitch tones that bounce off surfaces more. Prolonged loud high frequency noise above 2000Hz damages hearing ability first. Low frequency noise travels farther and through barriers. Knowing a noise’s frequency makeup helps select proper hearing protection and design quiet spaces by blocking high pitches and absorbing low rumbles. Frequency also relates to hearing loss and fitting hearing aids to amplify pitches a person can’t hear well. Overall, frequency determines a sound’s propagation and impact on hearing health.

What is Frequency?

Frequency refers to the number of oscillations or cycles per second of a sound wave. It is measured in Hertz (Hz), with 1 Hz equaling 1 complete cycle per second. The human ear can detect frequencies from 20 Hz at the low end of the audible range up to 20,000 Hz (20 kHz) at the high end. The frequency of a sound determines its perceived pitch, with lower frequencies below 250 Hz coming across as low bass notes and higher frequencies up to 8000 Hz being heard as high treble tones. Most speech frequencies fall between 85 Hz for a deep male voice up to 255 Hz for a high female voice. Frequency also impacts how a sound wave propagates. Lower frequencies below 500 Hz have longer wavelengths that diffract and bend around objects more easily.   Higher frequencies above 1000 Hz have shorter wavelengths that reflect and scatter more strongly.

How does Frequency impact hearing protection?

Understanding the frequency composition of noise sources is important for effective hearing loss prevention and noise control. High frequency noise above 2000 Hz damages the sensitive hair cells in the cochlea that transduce high frequency tones. This leads to difficulty distinguishing consonants and processing speech. Selecting proper hearing protection depends in part on a device’s ability to attenuate problematic high frequency noise while still allowing speech frequencies to pass through. Frequency spectra can also inform noise control techniques. High frequency noise is more effectively blocked by barriers and enclosures, while low frequencies require special materials and techniques to absorb and dampen vibrations.

Frequency in hearing devices

In audiology, frequency is analyzed to detect hearing loss and fit hearing aids. An audiogram charts the faintest tones a person can hear at different frequencies to identify deficient ranges needing amplification. Hearing aids then selectively amplify sound in frequency bands set to match the individual’s hearing loss profile. Understanding the components of the frequency spectrum is thus essential for protecting hearing, evaluating impairment, and improving perception.