How Does Sound Travel Underwater

How does sound travel through water? Is there some kind of wave going through the water or is it something else?

The ocean covers 71% of our planet and contains nearly 70% of its surface area. This makes it the largest reservoir of liquid water on Earth. Yet despite its size, scientists don’t fully understand how sound travels through water.

Sound waves propagate throughout water in three modes: (1) compressional waves, (2) shear waves, and (3) transverse waves. While each mode has unique properties, they share common characteristics. For example, both compressional and shear waves require pressure gradients to exist over time. But while a compressional wave requires a constant pressure gradient, a shear wave can be generated from any velocity difference between layers. In addition, all three types of sound waves are capable of transmitting energy at different frequencies. The transmission of energy depends upon the type of sound wave as well as the frequency of that wave.

How far does sound travel in the ocean?

There have been several studies that have attempted to measure the distance that sounds will travel in the ocean. These experiments were conducted using hydrophones, which are sensors that detect acoustic signals. Hydrophones are placed in an environment, and then researchers record the signal strength of the sound waves when they reach the sensor. Based on these measurements, scientists can determine the distance that the sound traveled.

In one study, researchers used two hydrophones located approximately 1 kilometer apart in order to measure the speed of sound in seawater. They found that the average speed was 1450 meters per second. However, this measurement only represents the average speed of sound in seawaters with salinities up to 3.5 percent. When the salt concentration increases above 3.5 percent, the speed of sound decreases significantly. At higher concentrations, the speed of sound is about 1230 m/s.

In another experiment, researchers used hydrophones to measure the speed of acoustic waves traveling through seawater. They measured the speed of sound at various depths below the sea surface and calculated the depth where the speed of sound reached half of its maximum value. They found that the speed of sound decreased by 5 percent for every meter increase in water depth.

What happens if you don’t know how sound travels in water?

If we do not know what causes sound to travel in a certain way, we cannot predict the results of a particular experiment. If researchers want to find out how sound propagates in water, they need to answer the following questions:

• What causes sound to travel in water?
• Why does the speed of sound change depending on the density of the medium?
• How does the speed of sound vary based on frequency?

Although there are many theories regarding how sound travels in water, the most accepted theory is that a compressional wave is responsible for moving sound through the water. According to this model, sound moves from high-pressure regions to low-pressure regions. The pressure changes cause a compression or expansion of the surrounding liquid. This movement creates the wave pattern that carries the sound across the water.

The speed of sound varies because it depends on the temperature and density of the water. Temperature affects the speed of sound because it determines the viscosity of the liquid. Viscosity describes the resistance to flow due to friction. Water’s viscosity increases as its temperature decreases. Therefore, the lower the temperature, the faster the sound travels through the water.

The density of water also influences the speed of sound. Sound travels more slowly in denser liquids than in less dense liquids. This relationship between density and speed of sound is expressed mathematically as follows:

where ρ density (kg/m3)

c speed of sound (m/s)

v velocity (m/s)

What Do You Hear Underwater?

You may wonder why you hear different things under the water than you would on land. For example, you might hear the sound of your own heartbeat while swimming in the pool. Or, you might hear the noise of someone else’s snorkel during scuba diving. The reason for this phenomenon has to do with the properties of sound.

Sound Waves

When sound waves hit solid objects, such as walls, doors, windows, and furniture, these objects vibrate. These vibrations create sounds that can be heard. Sound waves move away from their source. As they move farther away, their amplitude decreases. The distance over which an object vibrates before making a sound is called the wavelength. Wavelengths in air are much longer than wavelengths in water.

Water absorbs sound energy very quickly. When sound waves enter the water, they lose about 90 percent of their energy. This means that only 10 percent of the original sound energy reaches the surface of the water.

This loss of energy explains why you cannot hear anything when you dive into a lake or ocean. The lack of sound energy reaching the surface of the water makes it impossible for you to detect any sound coming from below.

However, sound waves still reach the bottom of the lake or ocean and continue traveling downward. Even though the amount of energy lost by the sound waves at the surface of the water is great, some of the sound energy will eventually make its way back up to the top of the water column.

This return of sound energy is known as reverberation. Reverberation occurs when sound waves bounce off the bottoms of lakes and oceans. If the depth of the water is greater than the length of the sound wave, then the sound will not reflect back toward the surface. However, if the depth of the water equals the length of the sound, then the sound will bounce back upward.

If the sound bounces back toward the surface, then you will be able to hear it again. This is why you may hear the sound of your heart beating after you have been swimming in the pool for a few minutes.

How Does Sound Travel Underwater?

As mentioned earlier, the speed of sound changes depending upon the temperature and density of water. The temperature of the water also affects how long a sound wave takes to travel through the water. In warm temperatures, the speed of sound is slower than in cold temperatures. Also, the density of water increases as the temperature goes down.

The combination of all of these factors results in sound waves taking longer to travel through the warmer water. Thus, the time it takes for a sound wave to travel from one point to another becomes longer. Since the speed of sound is always constant, the distance traveled by the sound wave must increase. Therefore, it takes more time for the sound to travel through the water as the temperature drops.

The result of this increased delay is that the sound arrives at the surface of the lake or ocean later than it did when the temperature was higher.

Underwater Acoustics

The sound that travels through the water creates pressure waves that spread out across the surface of the water like ripples on a pond. These pressure waves cause a disturbance in the water. This disturbance causes other waves to form within the body of water. These new waves then affect the pressure waves causing them to change direction and shape. Eventually, the pressure waves become so weak that they disappear altogether.

When the pressure waves disappear, there is no longer any evidence of the initial sound wave. At this point, the sound has traveled through the water without leaving any trace behind.

The final effect of the sound waves is that they create an echo. An echo is the reflection of the original sound wave back toward the source. For example, if you are speaking with someone who is standing next to a wall, the sound waves generated by your voice will hit the wall first. Then the sound waves will bounce back toward your ears. This is called an “echo” because it sounds like the person is talking into a void.

Echoes can occur only in bodies of water. They cannot occur in dry land because the air acts as a barrier between the sound waves and the ground.

What Happens When You Swim in Water?

Swimming in water has several effects on the human ear. First, the water makes the air around your head damp. This means that the air inside your ear canal is less dense than normal air. As a result, the volume of air filling up your ear canal decreases. Because the volume of air is smaller, the amount of sound reaching your eardrum is reduced.

Second, the water absorbs some of the sound energy that reaches your ear. This absorption reduces the sound level coming into your ear.

Third, the water makes the sound waves travel faster. This means that the sound waves reach your eardrums sooner.

Fourth, the water makes the echoes produced by the sound waves travel farther away from the source. This allows you to hear the echoes better.

How Can I Hear Better Underwater?

There are three ways to make yourself able to hear better under water:

1) Wear Ear Plugs

Ear plugs prevent sound from entering your ear canal. If you wear ear plugs while swimming, the sound waves won’t be absorbed by the water. Instead, the sound waves will pass right through your head and enter your ear canal. Your eardrums will receive the full impact of the sound waves which should allow you to hear better.

2) Use Sound Attenuators

Sound attenuators work just like ear plugs but also reduce the intensity of the sound waves hitting your eardrums. In other words, they turn down the volume. Some sound attenuators have built-in microphones for receiving the underwater environment.

3) Use Hearing Aids

Hearing aids amplify the low frequencies of the sound waves. Low frequency sound waves are more easily heard when the surrounding noise levels are lower. By using hearing aids, you can increase your ability to hear under water.