Audiology Chapter 5 - Burger TCU

False Responses

Term: False Negative Responses Definition: Occur when the client does not respond, even though the stimulus was presented at a level that should have been heard by the test ear (TE). Circumstances include Malingering, Tinnitus, poor headphone or oscillator placement, or lack of experience with the test.

False Positive Responses

Term: False Positive Responses Definition: Occur when the client responds even though no tone was presented or the tone was not loud enough to be heard by the test ear (TE). Circumstances include Guessing, Tinnitus, Cueing from the audiologist, Tactile responses, or Cross hearing.

Cross Hearing

Term: Cross Hearing Definition: The phenomenon where a sound presented to the Test Ear (TE) is heard by the Nontest Ear (NTE), most realistically by bone conduction. This can cause NTE false positive responses.

Interaural Attenuation (IA)

Term: Interaural Attenuation (IA) Definition: The loss of intensity (in dB) of a sound that is introduced to one ear (via air or bone conduction) and is heard by the other ear.

AC Masking

Term: AC Masking Definition: The introduction of noise into the Nontest Ear (NTE) to keep it busy while testing the Test Ear (TE) with an air-conduction stimulus, used to obtain the "true" threshold when cross hearing is suspected.

Shadow Curve

Term: Shadow Curve Definition: An audiogram curve that appears to show better hearing results due to cross-hearing to the NTE when no masking is used. The unmasked result is a 'shadow' of the better ear's true threshold.

The Liar curve

White or Broadband Noise (Gaussian noise)

Term: White or Broadband Noise (Gaussian noise) Definition: Masking noise with equal cycles per second, covering a broad range of frequencies, that sounds like hissing. Not ideal for masking pure-tones.

Narrowband Noise

Term: Narrowband Noise Definition: Masking noise consisting of frequencies that are surrounding the test stimuli. It is the type of noise used for pure-tone masking.

BC Masking

Term: BC Masking Definition: The procedure of introducing masking noise to the Nontest Ear (NTE) via air conduction to eliminate it from the procedure when cross hearing is suspected during bone-conduction testing.

Shotgun Approach

Stupid approach 

Term: Shotgun Approach Definition: An unsophisticated method of masking where noise is simply introduced into the NTE. This approach risks using too little or too much masking.

Minimum-Noise Method

Term: Minimum-Noise Method Definition: A method used for screening; if the NTE can be masked and the TE threshold stays the same, it suggests true TE results. If the NTE is masked and there is no TE response, it means the NTE was contributing to the initial response.

Initial Masking (IM)

Definition: In diagnostic testing, Initial Masking refers to the minimum effective level of masking noise needed to prevent the non-test ear (NTE) from detecting the test signal. It is equal to the air conduction (AC) threshold of the NTE ($IM = AC_{NTE}$) and is also known as Minimum Masking.

Maximum Masking

a.     Maximum Masking – sound can lateralize from TE to NTE, so can masking noise from masked (NTE) to TE.

                                               i.     The highest level of masking that can be used right before overmasking occurs.

                                              ii.     M_{max =} BC _TE + IA - 5

Effective Masking

Term: Effective Masking Definition: The range of masking noise that can be applied to the NTE that extends from Minimum Masking (Initial Masking) to Maximum Masking (without over-masking).

Central Masking

a.     Central masking – small shift (increase) of threshold when masking is introduced into the opposite ear; usually 5 dB.

                                               i.     Elevation of threshold happens by inhibition that is sent down from auditory centers in the brain.

a.     Masking dilemma –

problem that can occur when over-masking is a possibility (ie: bilateral conductive hearing losses)

Overmasking

a.     masking noise of NTE is so loud that it crosses over and produces a masking noise in the TE.

                                               i.     EM _NTE > BC _TE  + IA

Plateau Method (Hood, 1960)

a.     Plateau Method – (Hood, 1960)

                                               i.     Begin with IM (+ correction, if needed)

                                              ii.     If not heard, NTE was responding

                                             iii.     TE threshold must be found, by increasing TE tone with contralateral masking until the threshold is reestablished.

                                             iv.     Masking is increased in 5dB steps, while maintaining the same TE threshold for a total of 3 times.

                                              v.     Inserts:

1.     Decrease chances of overmasking

2.     Widen the masking plateau

Speech Noise

Term: Speech Noise Definition: The type of noise used for speech masking. It is a broadband noise that is filtered to resemble the speech spectrum (more energy in low frequencies than white noise).

Malingering

Definition: A circumstance that may cause a false negative response in the test ear.

Tinnitus

Definition: A circumstance that may cause either false negative responses or false positive responses in the test ear.

Guessing

Definition: A circumstance that may cause a false positive response in the test ear.

Cueing from an audiologist

Definition: A circumstance that may cause a false positive response in the test ear.

Tactile responses

Definition: A circumstance that may cause a false positive response in the test ear.

AC Interaural Attenuation

Definition: Interaural attenuation when the stimulus is delivered via air conduction (AC) to the test ear, but travels to the bone conduction (BC) of the non-test ear (NTE).

AC IA via A/C headphones

Definition: The interaural attenuation value for air-conduction using headphones is 40dBHL.

AC IA via A/C inserts (clinically)

60dB

AC Masking Formula (when to mask)

Definition: The rule to determine when cross hearing is a danger and masking is needed for air-conduction testing:

BC IA

0dBHL

BC Masking Formula (when to mask)

Definition: The rule to determine when cross hearing is a danger and masking is needed for bone-conduction testing: