Masking the ABR (1/2): Introduction to Masking

Summary

This video explains the concept of auditory masking in hearing tests. It describes how masking sounds are used to isolate the test ear and prevent cross-hearing from the non-test ear, ensuring accurate threshold measurements. The speaker highlights the importance of adjusting the masker level and how it affects the threshold on the test ear. It also discusses two scenarios: one where the threshold remains unchanged, and another where the threshold shifts due to cross-hearing. The video concludes with an introduction to masking considerations for Auditory Brainstem Response (ABR) testing.

Takeaways

• 😀 The masking procedure helps ensure accurate threshold measurements by preventing cross-hearing from the non-test ear.
• 😀 If the non-test ear cannot pick up the sound, the threshold measured in the test ear remains unaffected, resulting in a flat masking function.
• 😀 A flat masking curve on the chart indicates that the threshold measured is the true threshold of the test ear, without interference from the non-test ear.
• 😀 If sound waves cross over to the non-test ear, the threshold measured may be a shadow of the true threshold in the test ear, requiring masking to correct this.
• 😀 Masking the non-test ear during threshold measurements helps avoid misinterpretation of the results and ensures the integrity of the testing process.
• 😀 Increasing the masker level on the non-test ear gradually prevents it from responding to the sound, allowing the test ear's true threshold to be revealed.
• 😀 Once masking reaches a level where no further changes occur, the threshold of the test ear is accurately measured, and this level is recorded.
• 😀 The threshold measured with masking reflects the true hearing level of the test ear, free from interference by the non-test ear's ability to hear sound.
• 😀 Cross-hearing occurs when sound presented to one ear is perceived by the other ear, and masking helps isolate the response of the test ear.
• 😀 The process of masking is critical in ABR (Auditory Brainstem Response) testing to ensure that accurate results are obtained, specifically in cases where there may be cross-hearing.

Q & A

What is the purpose of masking in audiology testing?

Masking is used in audiology to ensure that a test ear's threshold is measured independently from the influence of the non-test ear. It prevents cross-hearing, where sound from the test ear is perceived by the non-test ear, potentially affecting the results.

What does the term 'true threshold' refer to in audiometry?

A true threshold refers to the accurate level of sound that the test ear can just barely detect without interference from the non-test ear. It is measured when the non-test ear is sufficiently masked.

How does the presence of masking sound affect the threshold measurement?

When masking sound is applied to the non-test ear, it ensures that the threshold measured for the test ear is not influenced by cross-hearing. If the test ear’s threshold remains unchanged despite increasing masking, it indicates a true threshold.

What happens if the threshold on the test ear changes when masking sound is presented?

If the threshold on the test ear changes when masking sound is presented to the non-test ear, it suggests that the original threshold was influenced by cross-hearing, indicating a false threshold due to the shadow curve from the non-test ear.

What is a 'shadow curve' in the context of audiometry?

A shadow curve occurs when sound from the test ear crosses over to the non-test ear, leading to a falsely low threshold measurement in the test ear. The masking sound prevents this cross-hearing, helping to clarify the true threshold.

Why is it important to gradually increase the masker level during testing?

Gradually increasing the masker level helps determine the point at which the masking sound completely inhibits the non-test ear’s ability to perceive the test sound. This ensures that the measured threshold for the test ear is accurate.

How does the schematic of the masking chart help in determining the true threshold?

The schematic of the masking chart illustrates how the threshold for the test ear behaves as the masker level is increased. A flat line indicates no cross-hearing, confirming a true threshold, while changes in the threshold suggest cross-hearing and the need for further masking.

What is the role of the ABR (Auditory Brainstem Response) in audiometry?

The ABR is a technique used to measure the brainstem’s response to sound stimuli. It can provide important information about the hearing threshold, especially in situations where behavioral testing is not feasible, such as with infants or individuals who cannot respond to traditional audiometry.

What should happen when masking sound is applied to both ears during audiometric testing?

When masking sound is applied to both ears, the masker should prevent the non-test ear from perceiving the test signal. The threshold for the test ear should then stabilize, ensuring that the measurement reflects the true hearing threshold for that ear only.

How do audiologists confirm whether a threshold is 'true' or affected by cross-hearing?

Audiologists confirm a true threshold by applying masking sound to the non-test ear and observing whether the threshold in the test ear remains consistent. If the threshold changes in response to masking, it suggests that cross-hearing influenced the original measurement.