The human ability to hear is a complex sensory process allowing the brain to interpret mechanical vibrations traveling through the air. Scientists use established benchmarks to describe the typical performance of this system. These benchmarks define average hearing for a young, healthy person, generally an individual under the age of 25 without significant noise exposure. Sound perception is quantified along two independent dimensions: frequency (pitch) and intensity (loudness).
Defining the Metrics of Sound (Frequency and Intensity)
Frequency is the physical measurement of how often a sound wave repeats per second, perceived by the human ear as pitch. This measurement is expressed in Hertz (Hz). A higher number corresponds to a higher-pitched sound, such as a piccolo, while a lower number indicates a deeper pitch, like the rumble of thunder.
The second primary metric is intensity, which represents the power or amplitude of the sound wave. Intensity is perceived as loudness and is measured using the logarithmic decibel (dB) scale. Because the scale is logarithmic, a small numerical increase represents a vast increase in sound power; for example, a 70 dB sound is ten times more intense than a 60 dB sound. A normal conversation is approximately 60 dB, and sounds exceeding 85 dB can cause permanent damage after prolonged exposure, illustrating the rapid increase in power.
The Full Scope of Young Adult Hearing (The Numerical Range)
The average range of hearing for a young person spans a wide spectrum of both frequency and intensity. In terms of frequency, a young, healthy individual can typically perceive sounds ranging from 20 Hz to 20,000 Hz (20 kHz). The lower end, 20 Hz, represents the deepest bass tones, while the upper limit encompasses extremely high-pitched sounds.
The ability to hear the highest frequencies begins to decrease naturally as a person enters their late teens and early twenties, a process known as presbycusis. While the theoretical limit is 20,000 Hz, the maximum frequency most people in their twenties can detect is often closer to 15,000 Hz or 17,000 Hz. This gradual, age-related decline confirms why young people are used as the standard baseline for defining the full capability of human hearing.
The intensity range for a young person extends from 0 decibels up to approximately 120 decibels. The starting point, 0 dB, is defined as the normative “threshold of human hearing,” representing the softest sound the average young ear can detect. Sounds at 120 dB, such as a siren or a rock concert, are considered the threshold of pain, the upper limit the ear can tolerate before physical discomfort occurs. When a person experiences hearing loss, their threshold is elevated, meaning sounds must be louder than 0 dB to be audible.
How Hearing is Tested and Mapped
Hearing specialists utilize a standardized procedure to measure an individual’s hearing sensitivity against the established average range. The primary tool is the pure-tone audiometry test, conducted in a sound-treated room to eliminate external noise. During the test, the person listens to various pure tones at specific frequencies and signals when they first hear the sound, determining their hearing threshold.
The results are recorded on a graphic chart called an audiogram, which serves as a visual map of a person’s hearing ability. The audiogram plots frequency in Hertz along the horizontal axis and intensity in decibels along the vertical axis. The vertical axis is inverted, meaning the quietest sounds (0 dB) are at the top and the loudest sounds are at the bottom.
The plotted thresholds show the softest sound a person hears at each tested pitch, typically ranging from 250 Hz to 8,000 Hz, which encompasses most frequencies important for speech comprehension. If a person’s plotted line falls within the normal range, typically between -10 dB and 25 dB, their hearing is considered within the average expectation for a young adult. Any points plotted below this area indicate an elevated threshold, suggesting a degree of hearing loss.