Answers to Questions on Auditory Perception

Effects of frequency on dB HL values

Q1. For the sounds in Exercise 2, what are the dB HL values if the sound was 500 Hz? How about 4000 Hz? Discuss why frequency does not impact dB SPL but does impact dB HL values. 

Q2. Patient X has a unilateral hearing loss in which the left ear is completely deaf, and the right has normal hearing. Patient Z has two ears with normal hearing. Sketch predicted MAF functions for these two listeners. Sketch predicted MAP functions for the left ear for both patients. 

Q3. Consider the impact of the following decisions as they apply to the staircase procedure for estimating threshold. Dis- cuss whether these decisions may affect the threshold or other test-related factors. 

a. Step size too big 
b. Step size too small
c. Starting level too high 
d. Starting level too low 

Q4. Auditory filters provide straightforward ways to determine how much a single tone will influence the detection of another tone. Using the auditory filter for a normal-hearing listener shown in Figure 3–11 (the 60-dB curve), calculate the level of the following tones that are passed through this filter. Using the numbers, discuss whether the 1500-Hz tone or the 2500-Hz tone will have a greater mask- ing effect on the 2000-Hz tone. Explain whether your calculations are consistent with upward spread of masking. 

a. 1500 Hz presented at 60 dB SPL 
b. 2000 Hz presented at 60 dB SPL 
c. 2500 Hz presented at 60 dB SPL 

Q5. Discuss the concept of upward spread of masking and explain why this concept might lead to problems with low- frequency amplification in hearing aids. 

Q6. Calculate the total power and the dB EML for a noise band 500 Hz wide centered at 2000 Hz with an LPC = 30 dB SLP. Do the same for a noise band that is 5000 Hz wide and centered at 2000 Hz. Discuss which of these noises is a more effective masker. After that discussion, consider whether one of these maskers is more efficient at masking than the other. Discuss the factors that you considered.

Q7. Using loudness growth functions, deter- mine how much louder a 50 dB SPL sound is than a 30 dB SPL sound. Is this the same relationship for 50 dB versus 70 dB SPL? Or 70 dB versus 90 dB SPL? (all have a 20 dB range). Discuss. In your answer, be sure to consider the implications of the units for loudness: a sound at 4 sones is twice as loud as a sound at 2 sones, and a sound at 8 sones is twice as loud as a sound at 4 sones. 

Q8. You are going to a concert next week, and you expect that sound levels will exceed 100 dB SPL. To protect your hearing, you purchase a set of musicians’ ear- plugs, which have a constant attenuation of 25 dB at all frequencies. 

a. Using the equal-loudness contours given in Figure 4–5, discuss whether these earplugs will change the natural loudness relationships across frequency that will occur in the concert. 

b. Your friend purchases foam earplugs with the following attenuation characteristics (Table 4–1). Do you expect that he will have the same experience at the concert that you will? Again, use the equal-loudness contours to dis- cuss. Consider, in particular, whether his perception will be dominated more by low or high frequencies. 

Q9. Provide three different examples indicating why loudness and intensity are not interchangeable terms.

Q10. Discuss the advantages and disadvantages of measuring temporal processing using gap detection versus the TMTF. In your answer include which of these methods might be more appropriate in a clinical setting? 

Q11. Loudness is subject to temporal integration. Sketch data for loudness as a function of stimulus duration that you predict would be consistent with temporal integration. 

Q12. The multiple looks experiment showed that thresholds decreased by 3 dB for the detection of two-tone pulses compared with one. If the threshold for one tone pulse was 50 dB SPL, sketch predicted thresholds for 1, 2, 4, and 8 tone pulses (all separated by the same amount, per- haps 20 ms). 

Q13. Describe how the place code works for pure tones. Can the place code work at high frequencies, low frequencies, or both? 

Q14. Describe how the temporal code works for pure tones. Can the temporal code work at high frequencies, low frequencies, or both? 

Q15. In your own words, explain the temporal theory for encoding the pitch of a harmonic complex with a fundamental frequency of 100 Hz. How might this theory explain the pitch of a harmonic complex that does not contain energy at 100 Hz but has a 100-Hz fundamental frequency?

Q16. A variety of hearing aid algorithms have been developed to help listeners with hear- ing loss better understand speech. One of these technologies is a frequency-lowering hearing aid, which essentially takes high- frequency sounds that are inaudible and transposes (lowers) the frequencies so that they can be presented in a region of usable hearing. Considering what you have learned about pitch perception, what are your predictions on the pitch of sounds if they are processed by a frequency-lower- ing aid? Using the information you have just provided, address whether you would recommend a frequency-lowering aid to a musician. Consider: 

a. if pitch is based on a place code
b. if pitch is based on a temporal code 

Q17. Discuss the three primary advantages of having two ears and how each of those advantages facilitates listening in every- day environments. 
-Ability to understand the speech in a background noise

Q18. Describe why ITDs are only useful for low-frequency sound localization and why ILDs are only useful for high- frequency sound localization. 

Q19. Describe the difference between the better- ear advantage and binaural squelch.