Do you know about sound? 🔊

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Speaker 1: You're listening to sleep Tight Science. Do you know what is louder than a car horn? The cry of a human baby? What which is about one hundred and fifteen decibels? Hello, friends, and welcome back to sleep Tight Science, a bedtime show that answers your questions about science. What do you think sound is a simple definition for us is that sound is anything that can be heard. My voice, the background music, the barking of a dog, rain or other weather, and your alarm in the morning are all sounds. In this episode, we will start to learn all about the science of sound and try to answer some of the questions that our listeners have submitted about this topic. Before we answer some of the questions, let's learn some basic facts. First, three things need to happen for a sound to be made and heard. First, an object vibrates is a type of energy made by vibrations. A vibrating object makes tiny, very fast back and forth movements. When that object vibrates, it causes movement in the air particles. These particles bump into the particles close to them, which makes them vibrate too, causing them to bump into more air particles. This movement called sound waves. Keeps going until they run out of energy. You hear the sound if your ear is within range of the vibration. For example, when a musician strums guitar strings they vibrate. The vibration moves the surrounding air and produces waves of sound. To picture a stone thrown into a still body of water, the rings of waves made by the stone hitting the water go on and on or expand indefinitely. The same is true with sound. Irregular repeating sound waves, or waves that do not have a regular pattern, create noise. In contrast, regular repeating waves produce musical notes. When the vibrations are fast, you hear a high note. When the vibrations are slow, it creates a low note. Second, the sound waves pass into a medium. A medium is any substance through which the waves can travel. Sound waves may travel through many mediums, such as air, water, and solid objects. Sound waves can pass through mediums in all directions. The properties of a sound wave change when it travels through different mediums. Gas an example is air. Liquid, an example is water or solids. An example is a bone. When a wave passes through a denser medium, it goes faster than it does through a less dense medium. This means that sound travels faster through water than through air, and faster through bone than through water. Third, some kind of receiver, such as a person's ear, picks up the sound waves. The ear changes the sound waves into signals that travel to the brain. The brain understands these signals as sound. Speaking, as well as hearing, involves vibrations. To speak, we move air past our vocal chords, which makes them vibrate. We change the sounds we make by stretching those vocal cords. When the vocal chords are stretched, we produce high sounds. When they are loose, we make lower sounds. This is known as the pitch of the sound. The sounds we hear every day are actually collections of simpler sounds. A musical sound is called a tone. If we strike a tuning fork, it gives off a pure tone, which is the sound of a single frequency. But if we were to sing or play a note on a trumpet or violin, the result would be a combination of one main frequency with other tones. This gives each musical instrument its characteristic or unique sound. Before we continue with the questions about sound, we thought we would share some of the facts we have collected that haven't made it into an episode. A few of these are really stinky. Did you know that some perfumes have whale poop in them, and that you can buy a perfume that smells like bacon, which might not actually be that bad. Did you know that butterflies taste food with their feet. I hope their feet are clean. A honey bee's wings move up and down two hundred and thirty times a second. It takes twelve bees their whole life to produce a single teaspoon of honey. Think of that the next time you have a bit of honey. Herrings, which are beautifully colored. Fish talk to each other by farting. How would you say hello in their language? Did you know that the closest relatives of the dinosaur Tyrannosaurus rex alive today are the chicken and the ostrich and the prehistoric snake called Titanoboa was over thirteen meters or forty two feet long and weighed as much as a car. Did you know that penguins shoot a stream of poop far away from the nest. They make so much poop that it can be seen from space. The poop and elephant produces in one day ways about the same as six six year old children. That certainly is a lot of poop. Speaking of poop in space, an astronauts toilet fixes onto their bottom. The toilet works like a vacuum cleaner and sucks the poop and pee away. Their pea is then recycled to make clean drinking water ew. And now let's come back to today's topic with this fact. Did you know that astronauts cannot hear or talk in space? Sound waves can only travel through solids, gases, and liquids. They cannot pass through a vacuum. Space doesn't contain any medium for sound waves to travel, and it's full of vacuum, so astronauts cannot hear or talk to each other in space. They require a radio to listen and communicate. How do sound recordings work. Sound recording stores electrical signals that represent sound waves in a way that can be played back to reproduce the original sound. When sound travels through air, it forms waves of high and low air pressure. When these waves hit a human ear drum, they shifting pressure causes the ear drum to vibrate and send a signal to the brain. Modern sound recording methods detect sound vibrations and convert or change them into an electrical signal that can be stored and played later. The first actual method of recording sound was Edison's phonograph of eighteen seventy seven. Sounds were captured by a horn and used to vibrate a needle against a revolving cylinder. The needle cut a bumpy groove or indentation on the cylinder. When the cylinder was replayed, a needle following along the groove reproduced or replayed the original sound. In the early nineteen hundreds, sound recordings improve with the invention of microphones. Microphones turn sound into an electrical signal that can drive a groove cutting machine. The quality of the replayed sound, called the reproduction, was also improved by using electric loudspeakers or amplifiers instead of mechanical horns. Later, discs or records replaced cylinders. This increased the amount of music that could be recorded. Better groove cutting machines, playback needles, and more stable turntable speeds improved sound quality even more. Stereo sound, introduced in nineteen fifty eight, used at least two microphones. The resulting separation of sounds from using at least two microphones gives the listener the impression that they hear a live performance. Magnetic recording became popular in the nineteen fifties. Magnetic recorders store sounds using an electromagnet and magnetic tape. When recording, the electrical signal produces a shifting magnetic field in a coiled wire device called a head. Magnetic iron oxide particles in a tape line up with the field as the tape passes the head. This forms a magnetic pattern. When the tape is played, the varying magnetic field makes a current in the head. That current can be intensified to reproduce the original sound. Today, all almost all recordings are digital, meaning the recorded sounds are stored as sequences of binary numbers. A binary number is made up of only zeros and ones. The main reason for this is that from then on, whatever is done to the signal, from transferring it by radio to making it louder or storing it away, no noise is added. Digital data is also simpler to process and compress. Once compressed, it can be transferred quickly between media and stored easily. The data files that result from a digital recording can simply be stored and played back on a computer. Audio files can be streamed or transferred to your phone or other devices for playback. That's how you are listening to this very episode. Why is sound important? There are many reasons why sound is important, including communication. Some machines communicate with us by making a noise to let us know they have finished a job. Others make a sound to warn us of danger. Sound is a crucial mode of communication for humans and animals alike. We have created languages, dialects, expressive tones, and other means of distinguishing ourselves. These small details in our development have allowed us to work together to achieve greater things. Animals make sounds to let other animals know they are there and to warn other animals about danger. Some animals have ears that detect sound as they travel through air or water. These ears convert vibrations into nerve impulses that travel to the brain. Other animals, such as snakes, sense ground vibrations. Animals also use sounds to communicate and gather information about their surroundings. Sounds such as the noises of falling rocks or moving predators, can warn them of danger that might be close by. Some animals, such as bats, dolphins, and whales, use sound to steer or move around and locate food. They send out short bursts of high frequency sound and investigate the returning echoes. This is called echo location. It helps these animals detect prey and estimate its speed and direction. Humans also use sound to determine how far it is to distant objects. Using sonar, a device often on a ship like a loudspeaker, gives off intense pulses of sound. A computer analyzes the timing and direction of returning echoes to calculate the positions and sizes of objects. The time it takes for the pulse to return to us provides a more accurate reading of distance. Lastly, music is solely based on sound. If there is no sound, there is no music. Music has long been used to heal, entertain, and communicate messages. Can you imagine life without music? I can't. Listening to natural sounds and some types of music help us to relax and feel calm. Other types of music make us feel lively. We also enjoy singing together. The science of sound reminds us to stop, listen and feel the vibration. In a future episode, we might introduce the science of music fun facts. The loud noise you create by cracking a whip occurs because its tip moves so fast it breaks the speed of sound. Sound travels much slower than light, whether in the air or water. Light travels one hundred and eighty six thousand miles per second, while sound only travels seven hundred and seventy miles per hour. You often hear things after you see them. For example, you see the lightning before you hear the thunder Dogs can hear much higher sounds than humans, and bats and dolphins can hear sounds much lower than humans. Usually, animals with larger ears can hear much better than animals with smaller ears, and flies cannot hear at all. Dolphins can hear sounds underwater from up to fifteen miles away. Bats produce a series of high frequency clicks twelve thousand herts to one hundred and fifty thousand herts to find their way in the darkness of night, and they have highly sensitive ears that listen to the echoes. The eruption of Krakatoa, a volcanic eruption in Indonesia in eighteen eighty three, is believed to be the loudest sound in human hisay. It was heard across roughly eight percent of the whole world. Some jets can travel faster than the speed of sound. This is called breaking the sound barrier. The human ear can't hear some sounds, but they still affect our bodies. Some scary movies use these sounds, as they cause people to shake and feel nervous. The fear of noise is called acousticophobia, and the fear of music is called mellophobia. Most cows produce more milk if they are given music to listen to. Scientific experiments have looked at how different types of music can also affect how much milk they produce. If we yell for eight years, seven months, and six days straight, we can produce enough sound energy to heat a cup of coffee. One of our favorite facts about sound waves is that when they bounce off a surface, the vibrations are reflected and you can hear them again. This is what creates an echo. The three smallest bones in our bodies are in the ear, and they help us to hear sounds. They are called the hammer, the anvil, and the stirrup. Together they are about the size of a pee we covered a lot in this episode. We learn that for sound to be made and heard, three things need to happen. And object vibrates. Second, the sound waves need to pass into a medium or a substance that they can pass through. Third, we need some kind of receiver to pick up the sound waves. We also talked about sound recordings and found out how these work, using things such as a telegraph, tapes, CDs and records, and digital recordings. We finished by discussing why sound is important to us and the world around us. I'd like to thank Dylan, Allie and Tiffany. We hope to have a chance to use your ideas in future episodes. If you'd like to send us your questions, please send them to Hello at sleep tip science dot com. Hm