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An audiogram is a standard graph used in audiology to represent an individual’s hearing ability across different frequencies. It visually displays the degree and type of hearing loss in each ear, helping audiologists diagnose hearing issues and plan appropriate interventions.

Purpose of an Audiogram

  • Hearing Assessment: Audiograms are used to evaluate an individual’s hearing sensitivity and identify any hearing loss.
  • Diagnosis: They help in diagnosing the type (conductive, sensorineural, or mixed) and degree of hearing loss.
  • Monitoring: Audiograms are used to monitor changes in hearing over time, particularly for individuals exposed to noise or those with progressive hearing conditions.

Components of an Audiogram

  1. Axes:
  • Horizontal Axis (Frequency): Represents the frequency of sound, measured in hertz (Hz), typically ranging from 250 Hz to 8000 Hz, which covers the most important frequencies for understanding speech.
  • Vertical Axis (Hearing Level): Represents the hearing level or intensity, measured in decibels (dB). It ranges from -10 dB (very soft sounds) to 120 dB (very loud sounds).
  1. Symbols:
  • Right Ear: Usually indicated by red circles (O) for air conduction and red triangles for masked air conduction.
  • Left Ear: Usually indicated by blue Xs for air conduction and blue squares for masked air conduction.
  • Bone Conduction: Represented by symbols such as < or > for unmasked and [ or ] for masked, often in black or green.
  1. Thresholds:
  • Hearing Threshold: The softest level of sound an individual can hear at each frequency, plotted for both air and bone conduction.
  • Normal Hearing Range: Typically considered to be between -10 dB and 20 dB across frequencies.

Types of Hearing Loss Indicated

  1. Conductive Hearing Loss:
  • Characteristics: There is a gap between air and bone conduction thresholds (air-bone gap).
  • Cause: Usually due to problems in the outer or middle ear, such as ear infections or blockages.
  1. Sensorineural Hearing Loss:
  • Characteristics: Both air and bone conduction thresholds are elevated, but without a significant air-bone gap.
  • Cause: Damage to the inner ear or auditory nerve, often due to aging, noise exposure, or genetic factors.
  1. Mixed Hearing Loss:
  • Characteristics: Both conductive and sensorineural components are present, showing an air-bone gap with elevated thresholds.

Interpreting an Audiogram

  • Normal Hearing: Thresholds between -10 dB and 20 dB across frequencies.
  • Mild Hearing Loss: Thresholds between 21 dB and 40 dB.
  • Moderate Hearing Loss: Thresholds between 41 dB and 55 dB.
  • Moderately Severe Hearing Loss: Thresholds between 56 dB and 70 dB.
  • Severe Hearing Loss: Thresholds between 71 dB and 90 dB.
  • Profound Hearing Loss: Thresholds above 91 dB.

Use in Clinical Settings

  • Baseline Assessment: Initial audiograms provide a baseline for future comparison.
  • Treatment Planning: Audiograms inform decisions about hearing aids, cochlear implants, or other auditory rehabilitation methods.
  • Legal and Occupational Screening: Used to assess hearing in contexts like workplace safety and legal evaluations of hearing impairment.

Audiograms are vital tools in audiology, providing a clear and standardized way to assess and communicate hearing abilities and losses, facilitating appropriate treatment and management of hearing conditions.

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