1. 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 PhysicalPsychological ------------------------------------- IntensityLoudness Frequency________ DurationLength

5. Intensity Decibel –Unit of measure of intensity –dB = 10logR (R=ratio) –dB = 20logR

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

7. Intensity Dynamic Range 1 10 100 1000 10000 100000 1000000 10000000 100000000 1000000000 10000000000 100000000000 1000000000000 10000000000000 100000000000000

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 1000000/1 10000000/1 100000000/1 1000000000/1 10000000000/1 100000000000/1 1000000000000/1 10000000000000/1 100000000000000/1

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 = -2.00000000001 = ? -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: 1 + 1 = 2 Integer: 1000 X 1000 = ? Log: 3 + 3 = 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 Integer: 1000000 / 100 = ? Log: 6 – 2 = 4 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 1cm 2 surface area SPL: amount of pressure exerted on a 1cm 2 surface area IL = SPL 2 dB IL =10logR equals dB SPL =20logR

19. dB Intensity Level Measure of energy Reference 1.0 X 10 -16 watts/cm 2 or.0000000000000001 watts/cm 2

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. dB IL =10logR or dB SPL =20logR Ratio No.Log dB IL dB SPL 1:1 1000 2:12.30103.06.0 3:13.47714.89.6 4:14.60206.012.0 5:15.69907.014.0 6:16.77817.815.6 7:17.84518.517.0 8:18.90309.018.0 9:19.95429.519.0 10:1101.00010.020.0

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)