The Hughson-Westlake Method of Obtaining Threshold

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Key Points

The Hughson-Westlake method specifies how you to obtain threshold. The key points are:

  • When the patient hears the tone, decrease the intensity 10 dB
  • When the patient does not hear the tone, increase the intensity 5 dB
  • You are seeking the lowest intensity at which the patient hears the tone at least 50% of the time.

Getting Started

Start by presenting an air-conduction tone in the better ear. We generally want to start testing by presenting a tone that the patient can easily hear. If the patient is normal hearing, a 1000 Hz tone at 30 dB HL is a reasonable starting point.

Why start at 1000 Hz, and 30 dB HL? When would 30 dB HL not be the starting level?

  1. 1000 Hz, a mid frequency, is a pitch that most people would think of when you tell them that you will present a tone. By starting at a mid frequency, rather than an extreme high or low frequency, the patient is less likely to be confused.
  2. Starting at 30 dB HL is arbitrary. In AudSim Flex the 'Threshold Assistant' starts at this level; however, an experienced audiologist does not always start at 30 dB HL.
    • The audiologist typically tries to presents a tone that is slightly above the predicted threshold. The audiologist will examine the past thresholds in deciding on the starting level, and uses information from the patient’s case history.
    • Some audiologists do not believe it is a good idea to present the first tone at an easy-to-hear level, and instead, present below-threshold tones, and increase the level rapidly until the patient responds. This may save time, and may minimize the amount of exaggeration of threshold that a person makes if he or she wishes to pretend that the hearing loss is worse than it actually is (if the person is simulating a non-organic loss)

What if the patient does not hear the first presentation at 30 dB HL?

If the first tone is not heard, the audiologist increases the intensity of the tone (often by 20 dB) to obtain the first response. If that tone is not heard, the audiologist will probably check to see if the patient has understood the directions before increasing the intensity further, as some times a patient will have heard the tone, but not have responded to it.

With the simulator, we recommend that if the 30 dB HL tone is not heard, that you present a 50 dB HL tone next. If that tone is not heard, increase the intensity in 10 dB steps until a positive response is obtained. Begin to predict the hearing thresholds by reading the case history.

Which ear is tested first?

You should test the better ear first. If there is no “better ear”, then it doesn’t matter. Having a routine, such as arbitrarily starting with the right ear if hearing is relatively equal in each ear, is a good practice that may make it less likely that you will make an error.

What is air conduction?

Air-conduction tones are presented through earphones and test the entire auditory system. Bone-conduction signals are presented through a bone-oscillator (also called bone vibrator), and send the signal to the inner ear. Bone conduction testing, if conducted, is completed after air-conduction testing.

The “Initial Descent”

In the “initial descent”, you are reducing the tone intensity to a level that is below threshold. You do not use these presentations when you are calculating whether the patient heard the tone. You begin your “counting” the first time the patient does not hear the tone (but only after the patient has provided you with one or more responses at that frequency).

Example

Assume the actual patient threshold is 5 dB HL.

  1. You present the tone at 30 dB HL and the patient hears it and pushes the response button
  2. You decrease the intensity 10 dB, to 20 dB HL, and present the tone. The patient responds.
  3. You decrease the intensity to 10 dB HL, and the patient responds.
  4. You decrease the intensity to 0 dB HL, and the patient does not respond.
    You have now completed the “initial descent” and start counting with the no response at 0 dB HL



The Up 5, Down 10 Rule

After you have made the "initial descent”, you increase the intensity in 5 dB steps whenever the patient does not hear the tone, and decrease it by 10 dB whenever the tone is heard. You have found threshold when you find the lowest level at which the person responds in at least 50% of three trials, and have verified that the patient does not respond to at least 50% of three trials at a level that is 5 dB lower.

Example -- A Perfectly Consistent Patient

Again, assume the actual patient threshold is 5 dB HL.

  1. The tone was not heard at 0 dB HL during the initial descent.
  2. You turn the tone up to 5 dB HL and present the tone. It is heard. (That’s 1 response / 1 presentation)
  3. Decrease the tone 10 dB to –5 dB HL, and present the tone. It is not heard. (0 / 1)
  4. Increase the tone 5 dB to 0 dB HL, and present the tone. It is not heard (0 / 2)
  5. Increase the tone 5 dB to 5 dB HL, and present the tone. It is heard. (That’s 2 / 2)

    6. Since the patient has 2 / 2 responses at 5 dB HL and 0 / 2 responses at 0 dB HL, you have obtained threshold = 5 dB HL.



Deciding if threshold has been obtained

If at one level, the patient hears the tone 2 / 2 times, and at the level 5 dB lower, the tone was not heard in either of 2 tries (0 / 2 responses), then that is threshold. Regardless of what happens on the third try, threshold would not change.

However, patients are not always perfectly consistent, and a third ascent will be needed.

  1. There was no response at 0 dB HL after initial descent.
  2. 5 dB HL – no response
  3. 10 dB HL – response
  4. 0 dB HL – no response
  5. 5 dB HL – response (there has now been a response in 1 of 2 presentations)
  6. -5 dB HL – no response
  7. 0 dB HL– response
  8. 5 dB HL – response (there have been 2 / 3 responses, this is threshold).

    9. At the level 0 dB HL, there were 0 / 3 responses. You know this is not threshold.)



The Order of Frequencies Tested

Typically, testing is conducted in the following order

  1. 1000 Hz
  2. 2000 Hz
  3. 3000 Hz
  4. 4000 Hz
  5. 8000 Hz
  6. 1000 Hz (Re-Test)
  7. 500 Hz
  8. 250 Hz

    9. Mid-octave frequencies are tested if needed. The better ear is tested first, then the poorer ear is tested.

What are mid-octave frequencies? When do they need to be tested

Doubling the frequency is an octave increase (e.g. from 1000 to 2000 Hz). When there has been a 20 dB or more difference in the thresholds at adjacent octaves, then the midoctave frequency should be tested. The midoctave frequency in this case is 1500 Hz. On the audiogram, the octave frequencies are shown with solid lines, the midoctave frequencies are usually shown with thinner or dotted lines.

Setting up for Bone-Conduction Testing

When doing (unmasked) bone conduction testing, start with the better ear, if one is significantly better. Starting with the better ear makes masking easier.
For the audiometer simulator programs, you should test both ears by bone conduction unless your instructor has told you otherwise.

How Bone-Conduction Testing Differs from Air-Conduction Testing

Threshold testing methods are the same in air- and bone-conduction testing. However, you cannot test 125 Hz, nor 8000 Hz. 6000 Hz is generally not tested.
The audiometer is not able to produce bone-conduction signals at as loud a maximum intensity as is feasible during air-conduction testing. If your patient has a severe or profound loss, you may find that you are marking “no response” fairly often.