How fast does sound travel

In determining the speed of sound in a given material, the material's stiffness and density tend to work against each other. While solids usually have a higher speed of sound than liquids because solids are stiffer than liquids, this generalization is not always true because density also plays a role.

While water is denser than air, its stiffness is enough greater than air to compensate for the high density and make the speed of sound greater in water. But the fact that sound travels faster in water than in air just brings up the next question: Why is it harder to talk to someone underwater than in air?

The answer is that sound couples poorly from air to water. When you talk, you do so by emitting air and then sending compression waves through this air. Your lungs provide the burst of air, and your vibrating vocal cords and mouth imprint the appropriate sound waveform on the air. In order for someone underwater to hear you, the sound waves have to go from the air in your mouth into the water surrounding you.

Hearing sounds through solids. If the sound is made directly within the solid and this travels directly to the ear then both reflection and absorption are reduced or eliminated. Thus putting an ear to a desk and making a quiet sound at the other end will demonstrate how well the sound will travel. Compare this with listening to the same sound through the air. Further examples of sounds travelling effectively through solids include listening to the central heating pump by placing a protected ear to a radiator, listening to a string telephone and putting an ear to the ground to hear the approach of horses hooves.

Sounds can travel at approximately metres per second in some solids and at a quarter of this speed in water. Note the sound speed minimum at meters. The decrease in sound speed near the surface is due to decreasing temperature. The sound speed at the surface is fast because the temperature is high from the sun warming the upper layers of the ocean. As the depth increases, the temperature gets colder and colder until it reaches a nearly constant value.

Since the temperature is now constant, the pressure of the water has the largest effect on sound speed. Because pressure increases with depth, sound speed increases with depth. Salinity has a much smaller effect on sound speed than temperature or pressure at most locations in the ocean.

This is because the effect of salinity on sound speed is small and salinity changes in the open ocean are small. Near shore and in estuaries , where the salinity varies greatly, salinity can have a more important effect on the speed of sound in water. It is important to understand that the way sound travels is very much dependent on the conditions of the ocean.

The sound speed minimum at roughly meter depth in mid-latitudes creates a sound channel that lets sound travel long distances in the ocean. Search for:. Home Science of Sound Sound What is sound? How do you characterize sounds?

Amplitude Intensity Frequency Wavelength How are sounds made? What happens when sound pressures are large? Sound Movement How fast does sound travel? Why does sound get weaker as it travels? Sound Spreading Sound Absorption How does sound move? Reflection Refraction Scattering Reverberation How does sound travel long distances?

Sound Measurement How is sound measured? What units are used to measure sound? How are sounds viewed and analyzed? How is hearing measured? What sounds can people hear? What sounds can animals hear?

Sounds in the Sea What are common underwater sounds? How does sound in air differ from sound in water? How do people and animals use sound in the sea? The temperature will affect the strength of the particle interactions an elastic property. At normal atmospheric pressure, the temperature dependence of the speed of a sound wave through dry air is approximated by the following equation:. Using this equation to determine the speed of a sound wave in air at a temperature of 20 degrees Celsius yields the following solution.

The above equation relating the speed of a sound wave in air to the temperature provides reasonably accurate speed values for temperatures between 0 and Celsius. The equation itself does not have any theoretical basis; it is simply the result of inspecting temperature-speed data for this temperature range. Other equations do exist that are based upon theoretical reasoning and provide accurate data for all temperatures.

Nonetheless, the equation above will be sufficient for our use as introductory Physics students. For this reason, humans can observe a detectable time delay between the thunder and the lightning during a storm. The arrival of the light wave from the location of the lightning strike occurs in so little time that it is essentially negligible. Yet the arrival of the sound wave from the location of the lightning strike occurs much later.

Another phenomenon related to the perception of time delays between two events is an echo. A person can often perceive a time delay between the production of a sound and the arrival of a reflection of that sound off a distant barrier.

If you have ever made a holler within a canyon, perhaps you have heard an echo of your holler off a distant canyon wall.

The time delay between the holler and the echo corresponds to the time for the holler to travel the round-trip distance to the canyon wall and back. A measurement of this time would allow a person to estimate the one-way distance to the canyon wall.

For instance if an echo is heard 1. The canyon wall is meters away. You might have noticed that the time of 0. Since the time delay corresponds to the time for the holler to travel the round-trip distance to the canyon wall and back, the one-way distance to the canyon wall corresponds to one-half the time delay. While an echo is of relatively minimal importance to humans, echolocation is an essential trick of the trade for bats.

Being a nocturnal creature, bats must use sound waves to navigate and hunt. They produce short bursts of ultrasonic sound waves that reflect off objects in their surroundings and return.

Their detection of the time delay between the sending and receiving of the pulses allows a bat to approximate the distance to surrounding objects. Some bats, known as Doppler bats, are capable of detecting the speed and direction of any moving objects by monitoring the changes in frequency of the reflected pulses.

These bats are utilizing the physics of the Doppler effect discussed in an earlier unit and also to be discussed later in Lesson 3.

This method of echolocation enables a bat to navigate and to hunt.