310
W.E Dolphin
a.
0.6 b.
1000
0.4
0
0.2
Q)
-1000
Q) 0.0
"0
"0
~
0.0
25.0
50.0
~
0
500
1000
1500
:!:
...
C.
c: 900 d.
E
C>
12000
ro
«
~ 600
1000
300
-10000
0
0.0
25.0
50.0
0
500
1000
1500
Time (msec)
Frequency (Hz)
FIGURE 7.9. Time (a) and frequency (b) domain representation of a two-tone stimulus signal comprised of tones F, =1,000 Hz and F 2 =1,171 Hz. In panels (c) and (d)
the corresponding time and frequency domain representations of the averaged
response recorded from the scalp surface of Tursiops truncatus. The major energy
in the response can be seen at 1,000 and 1,171 Hz (F, and F 2 ), the frequency following response (FFR), and at 171 Hz (F 2 .,), the envelope following response (EFR).
(Modified from Dolphin et al. 1995.)
signals is found at the modulation, or envelope, frequency of the stimulating waveform-a component not present in the original signal. This phenomena arises due to nonlinearities in the auditory system as indicated in
the block diagram shown in Figure 7.6. The EFR has been recorded in
humans (e.g., Kuwada 1986; Aoyagi et al. 1993; Levi et al. 1993), gerbils
(Dolphin and Mountain 1992; Dolphin et al. 1994), and cetaceans (Dolphin
et al. 1995,1996; Supin and Popov 1995c).
A system's temporal modulation rate transfer function (MTF) may be
determined as the magnitude of the response as a function of the stimulus
modulation frequency. The MTF is, therefore, a quantitative measure of
the degree to which the system can follow the envelope of a stimulating
waveform.
Dolphin et al. (1995) obtained MTFs from three cetacean species (T. truncatus, D. leucas, and P erassidens) using both sinusoidally amplitudemodulated as well as two-tone signals. MTFs from these cetacean species,
along with MTFs obtained from humans and Mongolian gerbils, have been
W.E Dolphin
a.
0.6 b.
1000
0.4
0
0.2
Q)
-1000
Q) 0.0
"0
"0
~
0.0
25.0
50.0
~
0
500
1000
1500
:!:
...
C.
c: 900 d.
E
C>
12000
ro
«
~ 600
1000
300
-10000
0
0.0
25.0
50.0
0
500
1000
1500
Time (msec)
Frequency (Hz)
FIGURE 7.9. Time (a) and frequency (b) domain representation of a two-tone stimulus signal comprised of tones F, =1,000 Hz and F 2 =1,171 Hz. In panels (c) and (d)
the corresponding time and frequency domain representations of the averaged
response recorded from the scalp surface of Tursiops truncatus. The major energy
in the response can be seen at 1,000 and 1,171 Hz (F, and F 2 ), the frequency following response (FFR), and at 171 Hz (F 2 .,), the envelope following response (EFR).
(Modified from Dolphin et al. 1995.)
signals is found at the modulation, or envelope, frequency of the stimulating waveform-a component not present in the original signal. This phenomena arises due to nonlinearities in the auditory system as indicated in
the block diagram shown in Figure 7.6. The EFR has been recorded in
humans (e.g., Kuwada 1986; Aoyagi et al. 1993; Levi et al. 1993), gerbils
(Dolphin and Mountain 1992; Dolphin et al. 1994), and cetaceans (Dolphin
et al. 1995,1996; Supin and Popov 1995c).
A system's temporal modulation rate transfer function (MTF) may be
determined as the magnitude of the response as a function of the stimulus
modulation frequency. The MTF is, therefore, a quantitative measure of
the degree to which the system can follow the envelope of a stimulating
waveform.
Dolphin et al. (1995) obtained MTFs from three cetacean species (T. truncatus, D. leucas, and P erassidens) using both sinusoidally amplitudemodulated as well as two-tone signals. MTFs from these cetacean species,
along with MTFs obtained from humans and Mongolian gerbils, have been