Audiology test one

• Audiologist


  Diagnose and non-medical management of hearing loss and hearing disorders/difficulties and diagnosing and treating balance disorders. Managing problems relating to auditory function and evaluating vestibular systems.

  
• Functions of the ear

  • Ear is input for language (other important sounds like music and safety)
  • Brain decodes information - listening is done by the brain
  • Strong connection between hearing and speech
  • Age of onset of hearing impairment in important

  
• Air conduction (AC)


  Outer ear, middle ear, inner ear and Auditory nerve

  
• Bone conduction (BC)


  Inner ear + auditory nerve

  
• Parts of the auditory system

  • Outer ear
  • Middle ear
  • Inner ear
  • Auditory nerve

  
• Conductive mechanism


  Outer ear + middle ear

  
• Sensorineural mechanism


  Inner ear + auditory nerve

  
• Retro cochlear pathology


  Problems with nerves or any part of the ascending auditory pathway (brain stem nuclei)
• The difference between air and bone conduction helps (by subtraction) identify hearing loss due to sound not being able to get through the outer and middle ear to cochlear (conductive hearing impairment) or the hair cells in the inner ear (sensorineural hearing impairment)

  
• New Zealand's audiogram symbols
• Wave


  A disturbance traveling through a medium by which energy is transferred from one particle of the medium to another without causing any permanent displacement of the medium itself
• Transverse wave


  NOT A SOUND
• Wavelength


  If frequency is how close together the wobbles are in time, then wavelength is how close together the wobbles are in space. Wavelength depends on the speed of sound (340 m/s in air at 15° C). Wavelength (λ) = speed of sound/frequency.

  
• Decibel scale


  A way to plot sounds without a large graph as the threshold of hearing is too high of a ratio between the quietest sound and loudest sound

  
• Sound level meters measure sound and spectral analysis is used to analyse complex waveforms

  
• Low pass filter


  Lets low frequencies get through but not high frequencies

  
• High-pass filter


  Lets high frequencies pass, but cuts low frequencies

  
• Band-pass filter


  Lets a band of frequencies pass, but cuts out the rest

  
• When a hearing loss exceeds the sound level of speech sounds, speech discrimination is impaired. The high-frequency consonants (such as /f/, /s/ and /th/) are usually the first to be affected.

  
• Components of a testing system that need calibration

  • The audiometer (oscillators, amplifiers, and attenuators)
  • The transducers (Supra-aural headphones, Insert earphones, Bone conductor and Free-field speakers)
  • The test booth or room (Noise floor, reverberation)

  
• Free field


  A sound field with no obstacles. In a free field, sound propagates from a source uniformly in all directions. The wave front is a sphere of increasing radius.
• If a wave encounters an object that is small relative to its wavelength λ, it will be transmitted with little or no change. If a wave encounters an object that is large relative to λ, the wave will be attenuated.

  
• Low frequencies wrap AROUND objects aren't blocked as much. High frequencies are BLOCKED easily.
• Sounds may follow multiple paths to meet the listener.
• Speech intelligibility is reduced in reverberant environments, as is directionality.

  
• Transmission loss is the difference in sound pressure level on either side of a barrier. Double the thickness increases TL by 6dB.
• Sabins = amount of lost sound.

  
• Pure tone audiometry


  Standard audiometric range = 250 Hz to 8000 Hz. This frequency range covers a range of frequencies present in speech sound, and we routine test at octave frequencies (and some inter-octave frequencies).

  
• Threshold of hearing


  Experimental procedures for finding thresholds are based on adaptive tracking procedures (need to adapt to different people's responses to the beeps).

  
• Decibel sound pressure level (dB SPL)


  A logarithmic scale that effectively compresses the range of sound intensities we can hear into a manageable range of numbers.

  
• The "Speech Banana" is the range of sounds on the audiogram scale.

  
• Descriptors for audiograms


  • Symmetry between ears: Symmetrical, Asymmetrical, Unilateral
  • Severity: often summarized by 4 freq. average; 0.5, 1, 2 & 4 kHz
  • Pattern: flat, gently sloping HF, steeply sloping HF, reverse slope, cookie bite, rising, notched
  • Configuration: Conductive (CHL) v Sensorineural (SNHL) v Mixed