Hearing ability exists on a wide continuum, making a single, universal definition for “deafness” complex. The term involves clinical measurement, functional communication challenges, and personal identity. Hearing loss is a spectrum, ranging from missing soft sounds to the inability to perceive even very loud noises. This article explains the clinical measurements and decibel thresholds audiologists use to define different levels of hearing loss, clarifying where the term “deafness” is applied.
How Hearing Is Measured
Hearing specialists quantify a person’s ability to hear by measuring two primary characteristics of sound: intensity and frequency. Intensity, or loudness, is measured in decibels (dB), a logarithmic unit reflecting sound pressure. On this scale, a 10 dB increase represents a tenfold increase in sound intensity, meaning small numerical changes reflect large differences in perceived loudness.
Frequency, or pitch, is measured in Hertz (Hz), where lower numbers represent bass tones and higher numbers represent treble tones. Human speech sounds fall predominantly between 250 Hz and 8000 Hz, making this range important in clinical testing. The softest sound a person can detect at a given frequency is called their hearing threshold.
These thresholds are plotted on a graph called an audiogram, the standard tool for diagnosing hearing loss. The horizontal axis displays frequency in Hz, and the vertical axis plots intensity in dB. A result of 0 dB on the audiogram means the individual can hear sounds at the same intensity as the average young, healthy ear.
The Spectrum of Hearing Loss Classifications
Clinicians use the hearing thresholds plotted on the audiogram to categorize the degree of hearing loss into standard clinical ranges. Hearing is considered normal if thresholds fall between -10 dB and 15 dB. People in this range can typically hear all speech sounds and quiet environmental noises without difficulty.
A Mild Hearing Loss is defined by thresholds between 26 dB and 40 dB. Individuals can generally follow a one-on-one conversation in a quiet environment but struggle with softer speech, such as a whisper, or understanding speech with background noise. Common sounds like a refrigerator humming may also be difficult to detect.
Hearing thresholds from 41 dB to 55 dB are classified as Moderate Hearing Loss. At this level, many everyday sounds become inaudible, and a person frequently needs others to repeat themselves, even in quiet settings. Normal conversational speech (typically around 50–60 dB) is often hard to hear without amplification.
A Severe Hearing Loss occurs when thresholds fall between 71 dB and 90 dB. Without amplification technology, a person with severe loss cannot hear regular conversational speech. Loud sounds like a vacuum cleaner or a ringing phone are often inaudible, and communication relies heavily on visual cues like lip-reading.
Defining Deafness and Profound Loss
The clinical definition of profound hearing loss is reached when hearing thresholds are 91 dB or greater. At this degree of loss, even extremely loud sounds, such as a motorcycle engine, may be difficult or impossible to hear. This profound loss is the point at which clinical “deafness” is applied.
The term “Hard of Hearing” (HoH) describes individuals with mild to severe hearing loss who possess residual hearing that can be utilized, often with amplification. In contrast, the term “deaf” is used for those with profound loss who have very little or no functional hearing. Those who are deaf often rely on specialized technology, such as cochlear implants, or visual methods like sign language for communication.
The distinction also carries social and cultural weight, separate from clinical measurement. “Deaf” (capital D) refers to individuals who identify with the linguistic and cultural community that uses sign language, viewing their deafness as a cultural identity rather than a disability. Conversely, “deaf” (lowercase d) refers to the audiological condition of profound hearing loss, regardless of cultural affiliation. In a clinical context, profound hearing loss (the inability to hear sounds quieter than 91 dB) is the measured degree that aligns with the most significant auditory impairment.