An ear trumpet is a cone-shaped shell, like a megaphone,
that was used before hearing aids were developed to help persons who were hard of
hearing. The small end of the cone was held in the ear, and the large end was aimed toward
the source of sound as in Figure 17.5. The ear trumpet increases the intensity of
sound because (a) it increases the speed of sound (b) it reflects sound back toward the
source (c) it gathers sound that would normally miss the ear and concentrates it into a
smaller area (d) it increases the density of the air.