Table 1.
Review of studies using conventional directional microphones (see text for details)
| Study | Subjects | Signal/Level/Azimuth | Noise/Level/Azimuth | Directional advantagc |
|---|---|---|---|---|
| Lentz (1972) | 20 adults Experienced w/HA Mild to mod-severe |
W-22 at 0 azimuth quiet; 0 and −6 dB SNR |
White noise at 62 dB SPL 180 azimuth |
17.5% at 0 dB 24.9% at −6 dB |
| Frank/Gooden(1973) | 20 normal in three studies (N = 60) | Rush-Hughes at 45 azimuth at 55 dB SPL quiet; +6; 0; −6; −12; −18 dB SNR |
MTB at 0 azimuth MTB at 180 azimuth MTB at 0 and 180 azimuth |
No directional advantage 15% at 0.–6, −12, −18 dB SNR 15% at 0, −6 and −12 dB SNR |
| Nielsen (1973) | 22 adults Experienced w/HA Mild to mod-severe |
PB words at 55 dB SPL at +5, +10, +15, +20 dB SNR | Cafeteria noise at 90. 180 and 270 azimuth | 17.2% and 18.2% at +5 and +10 dB SNR No advantage at +15 and +20 dB SNR |
| Sung/Sung/Angelelli (1975) | 32 adults Experienced w/HA Mild to mod-severe |
W-22 at 45 azimuth at 62 dB SPL | Cocktail noise at 225 azimuth at 62 dB SPL | DHA #3 = 8.9% re: Omni DHA #3 = 14.81% re: DHA #1 |
| Mueller/Johnson (1979) | 24 adults Experienced w/HA Mild to mod-severe |
SSI at 0 azimuth at 55 dB SPL | Connected dicourse presented overhead at 0, −10 and −20 dB SNR | 11.6% Aid D ≥ Aid A at 0 dB SNR 8.3% Aid D ≥ Aid A at −10 dB SNR 8.3% Aid D ≥ Aid A at −20 dB SNR |
| Madison/Hawkins (1983) | 12 adults normal hearing | NU-6 at 0 azimuth Adjusted in 2.5 dB steps for 50% performance |
MTB at 0 azimuth at 65 dB SPL Rt = 0 and 0.6 seconds |
10.7 dB at 0.0 sec Rt 3.4 dB at 0.6 sec Rt |
| Hawkins/Yacullo (1984) | 12 w/normal hearing 11 w/HL Experienced w/HA Mild to mod-severe |
NU-6 at 0 azimuth Adjusted in 2.5 dB Steps for 50% performance |
MTB at 0 azimuth at 65 dB SPL Rt = 0.3, 0.6 and 1.2 sec monaural and binaural |
MHI = 6.3,4.7. −0.6 dB at 0.3,0.6, 1.2 sec Rt BHI = 3.6,5.5, 1.5 dB at 0.3,0.6, 1.2 sec Rt MNH = 3.8,3.8, 1.3 dB at 0.3,0.6, 1.2 sec Rt BNH = 3.6,3.6,2.6 dB at 0.3,0.6, 1.2 sec Rt |
MTB = Multi-talker babble
SNR = Signal-to-noise ratio
DHA = Dircctional hearing aid
SSI = Synthetic Sentence Identification
Rt = Reverberation time
MHI = monaural hearing impaired
DHI = binaural hearing impaired
MNH = monaural normal hearing
BNH = binaural normal hearing