The study of sound perception is called pschoacoustics. Any time you hear or feel a how far does sound travel in the ocean?, there are some amazing things that happen.
Phase – the increase and decrease in pressure cycle any single vibration. Pitch is the term we use to describe the psychological sensation or perception of a sound by people. Pitch is sometimes confused with frequency, the term we use to describe the physical phenomena of sound energy created by a series of vibrations. These are two different but complementary aspects of sound perception. Typically, the first concept we introduce to beginners is the idea that sounds can be low or high, and that these sounds exist in a sound spectrum. Some animals hear lower than humans and some hear higher.
So this spectrum covers a wide range from . A science term for vibrations per second is Hertz, abbreviated Hz. What is the human range of hearing? What is human speech and noise? Loudness is a quality defined as the intensity of sound energy as it comes in contact with an eardrum or other surface. Another term describing loudness is amplitude. How do we measure sound intensity?
One bel is the ratio between the differences in intensity of two sounds of 10 to 1, and a decibel is one-tenth of a bel. Decibels are logarithmic in nature – a 10 decibel increases energy tenfold, so the difference between 60 decibels and 100 decibels is not 40 times, but 10,000 times as much energy! What happens as sound travels away from its source? How does the head effect sound waves?
1,000 vibrations per second further reducing their loudness as they travel across the head. For example, play your stereo and put a record jacket in between your head and speakers. It blocks high frequencies, the sound is duller. What’s the difference between high and low frequencies in terms of loudness? This cycle effects air pressure, increasing it, then decreasing it.
Scientists use positive numbers to describe the pressure increase and negative numbers to describe the decrease. Your brain is sensitive to a sound wave’s phase. Based on the subtle differences in a sound wave’s phase between your two ears, your brain can tell what direction a sound came from. Phase can be a regular pattern, like in a musical tone, or it can be irregular, like in a waterfall. How Do We Know What Direction a Sound Comes From?
How does the loudness of a sound effect the way we locate the direction of that sound’s origination? Our auditory pathway rapidly calculates the difference in loudness between the sound as it enters both ears. In other words, a sound coming from your left side has less energy and is slightly softer by the time it reaches your right side. What other phenomena effect the way we perceive sound?
For example, a parent seemingly ignores their screaming baby while you may notice it. What Does Distance Have to Do with Sound Perception? Sounds have different charactoristics based on how near or far they are heard from their source. All sound has a unique echo pattern created and shaped by its physical environment, whether it’s an ocean, subway, or phone booth. 1,000,000 times from its original level. 6 seconds in an average living room, 1-2 seconds in an average concert hall.
How do we know how big a room or space is based on its sound characteristics? Any space or listening environment has its own unique sound characteristics based on reverberation time and timbre. For example, why does a honking horn sound different in an open field vs. Each sound has a unique echo signature based on the size and shape of the space it occurs in. For example, a gymnasium or the Grand Canyon will have much longer reverberation times than a living room because the sound bouces back and forth over a much larger area.
Timbre is the most complex quality of the six to understand, much less teach to someone. It combines the concepts of frequency and loudness through time. There is also an entire set of mathematics that supports these concepts related to the harmonic series. A Cello plays a low C – note that in practice all of these tones sound at the same time! The lowest sounding tone is called the fundamental partial, in this example a Cello’s low C. It is the loudest tone of the series and the one we usually identify in music. The point of all of this is that the difference in the loudness through time of these frequencies that we perceive as timbre.
However, the effects of the air column in the flute vibrating vs. In spite of this fact we may perceive a musical passage as pleasant or unpleasant because music is a complex set of tones and tonal relationships. In spite of this fact we may consider some noises musical, like a crash cymbal or tubular bell! Hertz, the loudness of all its component frequencies, in terms of decibels the frequency and loudness through time, in terms of seconds. Fourier analysis is used by scientists for a range of research in the field of acoustics. By popular demand, I have added this activity page as a follow up to my Math, Science and Sound program. You will find that it focuses on the physics of sound and is organized into two main sections: Waves and Frequency.
My recommendation is to have your students work from top to bottom since the topics flow in a logical sequence. I start by recapping some of the key points from my presentation, then I follow up by including extended activities with sounds, animated graphics, and fun facts. Lastly, if you are a student, you have my permission to use any of my artwork, tables or graphics for a school science fair project. Waves: Sound travels through the air in waves. Waves: Standing Waves Activity Waves: Sound waves can be soft or loud. Waves: How fast do sound waves travel?
Sound is a form of energy. It travels from one place to another through a medium like air. It can also travel through other gases such as helium, and can even travel through liquids and solids. The only thing sound cannot travel through is a vacuum like space. When an object moves back and forth, or vibrates, it pushes the air molecules next to it. As air molecules get compressed into waves, the energy is transferred from molecule to molecule until it is exhausted. Question: Is there sound in space?
Hint: Space is an empty vacuum with no air. Answer: Sound is a form of energy that travels through a medium like air. In space, there is no sound because there is no air. How can astronauts hear each other in the spacecraft? To see and hear how strings vibrate in fractions and produce sound, please see my activity on Standing Waves. Waves: Sound waves can be soft or loud.
Sounds can be soft or loud. This characteristic of sound is called amplitude or volume. Volume measures the amount of energy in sound waves. More energy will move more air molecules and will sound louder. Less energy will move fewer air molecules and will sound softer. To see a decibel chart with some familiar sounds, please see below. Question: What was the loudest sound ever described by humans?
Hint: It was produced by the most famous volcano in recorded history. Answer: In 1883, the Krakatoa volcano in Indonesia erupted and threw ash and stone 300 square miles. The explosive sound from this eruption was heard 3,000 miles away. That’s the distance from San Francisco to New York City. Question: What was the loudest animal sound ever measured? Hint: It was made by the largest animal on the earth.
Answer: Blue whale communication has been measured up to 188 decibels, making it the loudest recorded sound from a living source. These underwater sounds have been detected 530 miles away. Sound waves travel at different speeds depending on the temperature of the air. At 44 degrees Fahrenheit, sound travels approximately 1,100 feet per second, or 750 miles per hour. 2 football fields every second, or approximately 1 mile every 5 seconds. Question: If the air temperature rises, would sound waves travel faster or slower?
Hint: As the temperature rises, molecules bump into each other more quickly, allowing the energy from the sound wave to travel more quickly. Answer: As the air temperature rises, sound waves travel faster. For example, at 32 degrees Fahrenheit, sound waves travel through the air at 1,087 feet per second, or 742 miles per hour. However, at 100 degrees Fahrenheit, sound waves would travel at 1,163 feet per second, or 794 miles per hour! Question: Do sound waves travel even faster through liquids and solids? Hint: Molecules are pushed together more tightly in liquids and solids, allowing the energy of the sound wave to travel more quickly. Answer: Sound waves travel through liquids and solids much quicker than air.
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2 times faster in water, or approximately 1 mile per second. In a solid like iron, sound waves travel 15 times as fast, or 3 miles per second. Now, can you guess why people used to put their ear to the track to listen for approaching trains? Knowing that sound waves travel through the air at 1 mile every 5 seconds, you can estimate the distance of a thunderstorm with my Thunderstorm Stopwatch activity.
Frequency: Sounds can be low or high. Sounds can be low like a growling tiger or high like a chirping bird. This characteristic of sound is called pitch or frequency. Objects which vibrate faster produce a higher frequency, and objects which vibrate more slowly produce a lower frequency. The frequency of a sound is equal to how many times it vibrates each second.
2 inches long, however, if you stretched out a tuba it would measure 27 feet! Answer: Shorter instruments produce a higher pitch or frequency. Sound waves can travel, or vibrate, through a shorter tube faster than a longer tube. The faster sound waves vibrate, the higher the vibrating frequency will be. You will see and hear how this works later with the panpipes activity. If you would like to hear and play frequencies, check out my Tone Synthesizer. Frequency: What frequencies can different animals hear?
First, let’s start with your hearing. Humans can hear between 20 Hz – 20,000 Hz. However, some animals can hear lower or higher than humans. Please see the chart below to compare your hearing to some animals you may have studied.
Is the hippo just yawning or is it vocalizing sounds we cannot hear? Why does the giraffe seem so quiet? Why would a herd of elephants suddenly perk up their ears and begin running in one direction? Animals which use Ultrasound: Listed below are three animals that are predators and three that are prey. Bats eat moths, shrews eat grasshoppers, and cats eat mice.
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These relationships are based on their ability to interact using sounds above our hearing. Why do bats fly with their mouths open? They are vocalizing high frequency chirps that bounce or “echo” back to them. This form of navigation is called echolocation. A bat can fly through a dark cave and catch moths in mid-air using echolocation.
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Why do grasshoppers need to hear frequencies up to 50,000 Hz? Shrews are insect-eating animals called insectivores, and they use echolocation to locate crunchy little snacks like the grasshopper. Have you ever heard the phrase, “quiet as a mouse? It’s not that mice are quiet, it’s just that much of their communication is ultrasonic. Compare this to the hearing range of a cat and you will understand how high-frequency communication can be a survival strategy.
Question: What animal can hear the lowest frequencies? Hint: It is a migratory bird. Answer: Pigeons can hear frequencies as low as . 1 Hz, or one vibration every ten seconds! This allows pigeons to hear the infrasonic sounds of ocean waves breaking on the coastline.
By positioning their flight path according to coastlines, pigeons can accurately navigate long migrations. Question: What animal can hear the highest frequencies? Answer: Noctuid Moths can hear up to 240,000 Hz! For a moth, the most important job every night is to avoid being eaten by echolocating bats. After hearing a bat’s ultrasonic chirps, a moth will quickly fly away to get out of the bat’s detection range.
You can determine the difference in frequency by listening to the beat patterns from two sound waves. If you would like to make a musical instrument that plays different pitches or frequencies, try my Panpipes . Notice as the pipes get shorter, the pitch or frequency gets higher. This happens because sound waves can travel, or vibrate, a short distance faster than a long distance. To make an instrument that involves measuring water, check out my Water bottle Xylophone . When you add water to a bottle, the pitch or frequency gets lower. My favorite sounding homemade musical instrument is the Tubular Glockenspiel .
As you will see and hear, the longer you make each metal tube, the lower the pitch or frequency. Strictly speaking, it’s not the length of the metal tubing that determines the frequency, rather it’s the mass of the tube. If you are interested in making an instrument that is based Pythagorean fractions, check out my Fraction Tubes . Just like the panpipes above, as the tubes get shorter, the pitch or frequency gets higher.