1. Auditory demonstration : sound level and frequency Yang-Hann Kim

2. The unit of sound  Absolute units The unit of pressure = Pascal(Pa) = N/m 2 The unit of velocity = m/sec The unit of intensity = Pa ‧ m/sec = watt/m 2 The unit of energy = joule = watt ‧ sec  Sound Pressure Level (SPL) For the amplitude of the sound pressure, we use the sound pressure level (SPL or ). It is defined as SPL is measured in units of decibels (dB); is the reference pressure. is the average pressure, and log 10 is a log function that has a base of 10. is 20 μ Pa(20×10 － 6 N/m2).

3. Sound sensation: The Decibel scale ▼ Sound pressure level in several situations Can you expect the sound pressure level (dB) in this class room ? 1Pa (RMS value)  94dB Let us measure the sound pressure using sound level meter ! (Ref. : Brüel & Kjær Sound & Vibration Measurement)

4. Sound sensation : The Decibel scale Broad-band noise 6dB reduction 10 steps … Step 6 dB Broad-band noise 3dB reduction … Step 3 dB 15 steps Broad-band noise 1dB reduction … Step 1 dB 20 steps SPL(dB)

5. Frequency  Frequency is the number of occurrences of a repeating event per unit time.  Unit of frequency: Hz (cycles/sec)  Octave, 1/3 octave and 1/n octave

6. Sound sensation : Frequency response of the ear 125, 250, 500, 1000 2000, 4000, 8000 (Hz) ▼ Equal loudness contour ▼ Audible frequencies (Equal-loudness contour: ISO 226) 1252505001000200040008000 1 st 2 nd “Count the number of steps you hear.”  simulator

7. Sound sensation : Masking effect (a) masker: 1200Hz, test: 2000Hz relative amplitude Distance from stapes 1600Hz 400Hz 200Hz (b) masker: 2000Hz, test: 1200Hz 1200Hz 2000Hz Distance amplitude Distance amplitude 1200Hz 2000Hz  simulator

8. Sound sensation : Structure of the ear Outer ear Middle ear Inner ear pinna eardrumossicles semi-circular canals eustachian tube cochlea auditory nerve Function of Ossicles

9. Sound sensation : Frequency