Drinking cranberry juice is a fairly well-known and natural way to both help prevent urinary tract infections, as well as help speed the recovery process when a UTI develops. Just drinking two 4-ounce glasses of cranberry juice daily is often enough to both prevent a UTI and speed recovery when an infection does develop.
Ultrasound waves travel faster through a stiff medium, such as bone. In echocardiography, the velocity of sound is assumed to be approximately 1,540 m/sec (or 1.54 m/msec). Sound waves travel through the air with speed of 330 m/s.
As ultrasound is transmitted, there are parts of the wave that are compressed (increase in pressure or density) and parts that are rarefied (decrease in pressure or density). When used in diagnostic echocardiography, the frequency is usually above 20,000 Hz (20 kHz), and it is not audible to a human ear.