Masking

Question 1

When do you need to mask for AC ABR?

Answer 1

If Wave I absolute latency is prolonged (not needed if within normal range)
Or when stimulus intensity exceeds IA for inserts (approx. > 65-70 dB nHL)

Question 2

How do you mask for AC ABR?

Answer 2

For adults, 45-50 dB masking level fixed
Or use a masking calculator Masking level = stimulus level test ear – IA +RML
Available in some systems or at abrpeerreview.co.uk/resources.html or Lightfoot et al (2013)
Equation good for those <2-3 years of age, bilateral conductive and for supra-aural headphones
Don’t use contralateral masking >50-55 dB nHL due to potential for central masking

Question 3

When do you mask for BC ABR?

Answer 3

If wave I absolute latency is prolonged (not needed if within normal range)
If not present or delayed, masking needed on all adults
IA for adults is 0 dB; IA for children is 15-25 dB; IA for neonates 25-35 dB (bones not fully fused)

Question 4

How do you mask for BC ABR?

Answer 4

Adults: Fixed value not to exceed 45 dB nHL
Or use a masking calculator similar to AC