1. Perry C. Hanavan, Au.D. Audiologist
Sound Audiology
Perry C. Hanavan, Au.D.
Audiologist

2. Sound
Vibration
Perception

3. Propagation of Sound Condensations ____________
Example of molecular motion
Components of sinusoid
Transverse wave simulation
Applet: Square, triangle, simulation

4. Components of Sound Physical Psychological
Intensity Loudness
Frequency ________
Duration Length

5. Intensity Decibel Unit of measure of intensity dB = 10logR (R=ratio)

6. Problem Human hearing intensity dynamic range is quite broad
1 Softest sound
1,000,000,000,000 Loudest sound

7. Intensity Dynamic Range1 10
100
1000
10000
100000

8. Honey I Shrunk the Kids
1,3,5 or 1, 4, 8, 12 etc. reduces dynamic range somewhat
1, 10, 100, 1000 shrinks a bit more
Yet, dynamic range is quite large

9. Solution Ratio Compare intensity value (number) to reference
8:4 (really 2:1)

10. Aha! Ratio Compare 2 Numbers
1/1 =1
10/1 =10
100/1 =100
1000/1 =1000
10000/1
100000/1 /1 /1 /1 /1 /1 /1 /1 /1 /1

11. Logarithms!! Now that a ratio has been converted
Next step: Convert ratios to logs (base 10)

12. Lets Work with Logs!!! 1 = 0 10 = 1 100 = 2 100000000000000 = ? 14
.1 = -1
.01 = -2
= ?
-11

13. So is that a decibel? So far we have
1. Converted a ratio to a number (10:1=10)
2. Converted the ratio to a log (10=1)
We have created a ____ (A.G. Bell)
There are 10 decibels in a bel
2 bels = 20 decibels
8 bels = 80 decibels

14. WOW!!! Decibel = 10 log _____ A decibel consists of: 1. Ratio 2. Log
3. X10

15. That was easy, let’s practice:
Integer: 10 X 10 = 100
Log: = 2
Integer: X 1000 = ?
Log: = 6
Now take the log times 10 to convert to decibels

16. Not bad, let’s try this: Integer: 100 / 10 = 10 Log: 2 - 1 = 1
Now take the log times 10 to convert to decibels

17. Ok, I can do that, but…
Some numbers are quite easy to work with in logs
However, some numbers you need to use a calculator or look in a CRC book of tables
Or you can memorize several numbers and calculate lots of logs
Hint: log = bel

18. Oh, one more thing:
Measures of ________ are often made in Sound Pressure Level (SPL) rather than Intensity Level (IL)
IL: amount of energy flowing thru a 1cm2 surface area
SPL: amount of pressure exerted on a 1cm2 surface area
IL = SPL2
dBIL=10logR equals dBSPL=20logR

19. dB Intensity Level Measure of energy Reference 1.0 X 10 -16 watts/cm2or
watts/cm2

20. dB Sound Pressure Level
Measure of force or pressure
Reference
20 microPA

21. Ratios in IL and SPL Sound Pressure Level 20/20 = 1:1 40/20 = 2:1
60/20 = 3:1
200/20 = 10:1
Intensity Level
1.0x10-16/1.0x10-16
2.0x10-16/1.0x10-16
3.0x10-16/1.0x10-16
4.0x10-16/1.0x10-16
1.0x10-15/1.0x10-16

22. dBIL=10logR or dBSPL=20logR
Ratio No. Log dBIL dBSPL 1: 2: 3: 4: 5: 6: 7: 8: 9:
10:

23. Can you do this? Double SPL? Double IL? Triple SPL Triple IL?
Quadruple SPL?
Quadruple IL?

24. What about this?
Halve IL?
Halve SPL?

25. Practical Applications of dB
If a child’s ear canal is ___ times as small as an adult, what happens to the SPL in the child’s ear canal?
If a student is 3 times closer to the teacher’s voice than another, how much more SPL reaches the child sitting near the teacher?

26. Hearing Level
Converting SPL to HL (HTL)