The Thorp propagation model  is applied to explain the acoustic channel
in underwater communications.
Moreover, the major factors influencing in underwater MAC protocol design are man-made noise, Doppler frequency spread, transmission loss, inter-symbol interference (ISI) by multipath propagation, variable propagation delay and all these factors determine the spatial and temporal variability of the acoustic channel
. Researchers have developed numerous MAC protocols for underwater , , and hybrid variants have also been employed , .
However, underwater acoustic channel
(UAC) is one of the most challenging environments for the transmission of information due to the unique characteristics of the UAC such as limited bandwidth, high and variable propagation delays, and significant scattering and multipath.
In UAC, a doubly spread acoustic channel
(dispersion in time and frequency) is estimated by orthogonal matching pursuit (OMP) algorithm in [14, 15], which makes use of the sparse structure of channel impulse response.
To decrease the complexity for equalization in large latency underwater acoustic channel
, frequency domain channel equalization is presented in , but both of these are insufficient to avoid the short range issue owing to the serious attenuation.
The underwater acoustic channel
is generally recognized as one of the most challenging channels.
The novice underwater acoustic channel
model was illustrated in .
We begin by establishing an acoustic channel
suitable for confined underwater space.
argue that emotional facial expressions are during the actual production of emotional song, and in the perception, planning, and post-production of emotional song: facial expressions of emotion supplement the acoustic channel
of music, and can linger beyond the acoustic dimension of music.
The anti-noise signal y(n) can be modified by the secondary-path function H(z) in the acoustic channel
from y(n) to e(n), in this same way as the primary noise signal x(n) is modified by the primary path P(z) from the noise source to the error signal sensor.
Therefore, an acoustic channel
of communication could be functional at short distances.
Teachers of people who are hearing impaired are trained to use the acoustic channel
and view signing as an obstacle to the integration of deaf people into mainstream Hungarian society.