PowerPoint , (uncomfortable level, UCL) (dynamic range), ,
, 20 Hz , 20,000 Hz .
, . ( 53 dB SPL 77 dB SPL) , (consonants), ‘[s]' ’[t]' (phonemes) . (vowels) .



< 1-12>. ‘' '' 1 2

1


1


2


2

‘’
‘’
250
500
4
K
2
K
1
K
250
500
4
K
2
K
1
K

1


1


2


2

Hz

     (Byrne. et al., 1994). 90%, 75% 500 ~ 4,000 Hz (Macrae & Dillon, 1996). , . , , ‘ ’ ‘’ .
     , , .



< 1-13> (dynamic range): (A) , (B) (C)



















(B)
(A)
(C)







(A)
(B)


Hz
Hz
< 1-15> (A) (B) - ,


( ) ( ) (upward spread of masking)(Danaher & Pickett, 1975; Martin & Pickett, 1970) . (noise-induced hearing losses) (Shilling, et al., 1998). . , . , (Dubno & Shaefer, 1991).


( - forward spread of masking) ( - backward spread of masking) . . (Danaher, et al., 1978; Zwicker & Schorn, 1982). (Glasberg & Moore, 1989). . , . , (Hygge, et al., 1992; Peters, et al., 1998). , .

(A) Slow acting dynamic compression
(B) Fast acting dynamic compression

-

(SNR: signal to noise ratio) (Plomp, 1988). , 4 dB , 10 dB (Killion, 1988). .



< 1-18> (real ear insertion gain). (Boer, 1982) (Filler et al., 1945)
125
250
500
1K
2K
4K
8K
0
10
30
20
Frequency


< 1-20> (Western Electric Model 38-A Carbon hearing aid)
125
250
500
1K
2K
4K
8K
0
10
30
20
Insertion gain - dB
(carbon microphone), (magnetic receiver) . , . , . (coil) , .



1948 , 1952 Raytheon Company PNP (Skafte, 1990). 1953 , , , (binaural fitting) . . , (behind-the-ear, BTE type) , 1950 , (in-the-ear, ITE type) .

/
A/D converter


(earmold)
  
     . , , (, ) .(< 1-23> )
    
     (receiver) (vibrator) , (mastoid) . , (hair band type hearing aid) , , , (pinna) . .

   (analog)
     (conventional hearing aid) (programmable) . (software) .
   (digital)
     2 ‘0’ ‘1’ , . , .