Lecture 1.0 - Introduction and Pure Tone Audiometry Flashcards
What is sound?
Sound is a longitudinal pressure wave caused by an object’s vibration that disturbs the adjacent molecules.
The movement of molecules creates areas of high pressure (compressions) and low pressure (rarefactions).
True or False: The molecules in a sound wave travel to the human ear
False, the molecules stay in roughly the same place. They vibrate backwards and forwards.
How does sound intensity affect the movement of molecules?
The greater the intensity of the sound, the greater the distance the molecules move.
This relates to our perception of loudness.
How does the sound frequency affect the movement of molecules?
The higher the frequency of a sound, the greater the number of back and forward movements per second.
This relates to our perception of pitch.
What is the period of a wave?
The time taken for a pure tone to complete one cycle.
It is the inverse to frequency which is the number of cycles per second.
What is the wavelength?
The physical distance that is covered by a complete cycle of a sound wave.
The higher the frequency, the shorter the wavelength and vice versa.
What are the two ways we can measure the pressure of a sound wave?
- Peak amplitude
- Root mean square (RMS)
*We cannot calculate an overall average as the values would cancel each other out
What is a pure tone?
A pure tone is a sound that consists of one single frequency.
What is a complex sound?
A soundwave that is comprised of multiple different frequencies.
What is a harmonic structure of a wave?
A whole-number multiple of the fundamental frequency.
What is the phase of a wave?
A way to describe the starting point of a wave.
If a wave begins at 0 or 360 degrees, it is said to be in phase with the standard.
Tones beginning out of phase are discussed in terms of difference in degrees from the standard.
What happens when two tones of the same frequency, phase and intensity interact?
The amplitude is increased.
What occurs when two tones of the same frequency but are 180 degrees out of phase interact?
They cancel each other out (0 amplitude).
Used for noise cancelling headphones and hearing aids.
What is white noise?
A sound comprising of all the audible frequencies at once.
What is pure tone audiometry?
A behavioural test used to measure the threshold of hearing pure tones of different frequencies.
What is a behavioural test?
A test where a patient is asked to perform a certain behaviour in response to a cue.
What is the “threshold of hearing”?
The lowest level at which responses occur in at least one-half of ascending trials, with a minimum of two responses out of three presentations at a particular level.
Why is pure tone audiometry such an invaluable test?
- Most hearing disorders cause hearing loss
- It can lead to a diagnosis on its own
- Some hearing disorders produce audiograms that are nearly pathognomonic
- Has both diagnostic and rehabilitative value (can be used to track changes over time and set up hearing aids)
- Tests the full auditory pathway
What is the range of frequencies that humans can hear?
20 - 20,000 Hz
What is the standard audiometric range?
250 Hz to 8000 Hz
Why do we test the 250Hz to 8000Hz frequency range when we can hear beyond this?
This range focuses on the frequencies of daily life, including that of speech sounds
How and why might the high frequency range be extended?
Sometimes we will test 8000 Hz to 16,000 Hz.
This can occur if a patient is reporting high frequency hearing loss but it is not picked up on the standard range or if the patient has certain red flags (undergoing chemo therapy).
Note, some equipment may struggle to produce the extended frequency sounds.
How does tonotopicity relate to the ear?
cochlear and nerve bundles
What part of the cochlear is activated by high frequency sounds?
Base
What part of the cochlear is activated by low frequency sounds?
Apex
What are the strengths of using pure tones in the test?
- Due to the tonopicity of the cochlear, pure tones allow us to simulate discrete regions of the auditory system
- Using complex sounds stimulates multiple areas at once and would not allow us to know which parts are working and which are not.
- Some hearing disorders produce characteristic patterns of hearing loss (i.e., some frequencies are impacted over others)
- Pure tones are easy to calibrate and are consistent.
What are some disadvantages of using pure tones?
- They do not have high face validity (does not match sounds in the real world)
- To counter this, we add in more tests which do have high face validity (speech audiometry)
What are some factors that can impact behavioural tests?
- Patient understanding and co-operation
- The instructions given by the audiologist
- Dexterity
- Fatigue
- Recent noise exposure
- Reaction time of the patient (a long reaction time can make it seem like they didn’t hear it).
- Comorbidities e.g., tinnitus
What are the three types of responses that can occur?
- True positive = patient correctly presses button at the right time and duration
- False positive = Patient responds when no signal was presented
- False negative = Signal heard, patient did not respond
*It is important to observe the patient for signs of hesitation, button hovering and wincing.
What are some considerations when threshold seeking?
Time and simplicity.
However, making changes based on these considerations can sometimes come at the cost of accuracy.
What does adaptive mean in regards to threshold testing?
We have not predetermined the frequencies and amplitude settings. We change it as we go based on the responses of the client.
What is the clinical procedure used in threshold testing?
Modified Hughson-Westlake Technique
