welcome to the physics classroom's video tutorial on sound waves the topic of this video is properties of sound waves and we want to know what do the various properties of sound waves like frequency amplitude wavelength and speed describe I'm Mr H let's get started an understanding of the properties of sound waves begins with the basics with an understanding of the nature of a sound wave I discussed this topic in a previous video this one and I've left a link to the video in the Des description section of this one if you need to review it I'm going to highlight four main points from that video that will form the foundation for understanding the properties of sound waves the first one is that sound is created by a vibrating object and it's the vibration of this this object that forces disturbances into the medium that begin to move from one location to another location second sound is a mechanical wave that propagates or moves through a medium by means of particle to particle interaction the vibrations of the source force a particle within the medium to vibrate about a fixed position that particle interacts with its neighbor forcing it to vibrate about a fixed position which then interacts with its neighboring particle forcing it to vibrate about a fixed position the wave propagates the medium by means of this particle to particle interaction third in fluids such as air sound travels as a longitudinal wave there's no no Crest or trough in a sound wave instead there's regions where the particles are pressed together and we call the these compressions in other regions where they're spread apart and those are referred to as rare factions this pattern of alternating compressions and rare factions is what we observe moving through the medium finally a soundwave transports energy from one location to another without actually moving physical matter from the source to the surrounding area frequency is one property of a sound wave in general the word frequency refers to how often a periodic and repeating event repeats itself it indicates the number of times the event occurs per second or per minute per day per year if the event happens to be the orbit of the earth about the sun we would describe its frequency is one time per year for waves the event happens to be a vibration of a particle about its fixed position so for sound waves frequency refers to how often a particle repeats one complete back and forth vibrational cycle we measure in cycles per time such as cycles per second an equivalent unit would be the unit Hertz abbreviated HZ one thing you can be certain of is that the vibrational frequencies of the particles of the V medium are perfectly synchronized with the vibrational frequencies of its source so if the source of a sound wave is a tuning fork vibrating back and forth then you can be certain that if the tin of the tuning fork vibrate back and forth 260 times per second then every particle the medium will vibrate back and forth 260 times per second a sound's frequency is perceived as its pitch a quality of sound that many of us are familiar with a high pitch sound is perceived of a high frequency sound wave and a low pitch sound is perceived of a low frequency Soundwave humans can typically hear frequencies that are as low as 20 HZ and as high as 20,000 Hertz this is referred to as the audible range of human hearing a sound with a frequency less than 20 Hertz is an infrasonic sound and a sound with a frequency greater than 20,000 Hertz is an ultrasonic sound sound travels through fluids such as air as a longitudinal wave the particles of the medum vibrate back and forth in a direction that is parallel and anti-parallel to the direction that the wave is traveling so if a wave is traveling from a tuning fork as its source to from left to right particles of the medium vibrate back and forth left to right and right to left this creates compressions and rare factions within the medium this pattern of compressions and rare factions what is what we observe moving from The Source the surrounding regions the amplitude refers to the maximum displacement of a particle from its rest position so if I were to isolate a single particle and watch it vibrate from rest to a far right position and then back to a far left position and back to a far right position and so forth we would describe the amplitude as being the distance from the rest position to the far right position or from the rest position to the far left position now if I were to whisper the particles the medium would vibrate with a small amplitude I'd be putting very little energy into the way there'd be very small amplitude and you would perceive it as a soft not loud sound but if I were to holler I would be putting a lot of energy into the wave we would observe the amplitude to be significantly greater and that sound would be perceived as a loud or intense sound so high amplitude sounds are associated with sounds that transport a lot of energy and are perceived as loud intense sounds in general wavelength is the length of a wave it's the length of the repeating unit that's observed within the wave pattern we typically think of it as the distance from Crest to Crest or the distance from trough to trough but longitudinal waves like a sound wave moving through air don't have crests and troughs instead they have compressions and rif factions here we see a diagram of a l itudinal wave moving through a Slinky and the wavelength could be thought of is the distance from one compression to the next adjacent compression or just as equally the distance from a rare faction to the next adjacent rare faction wavelength and frequency are inversely related to one another a high frequency sound wave is a short wavelength wave and a low frequency sound wave is a long wavelength wave the speed of sound like the speed of any object object is the distance traveled per unit of time it's the distance a compression of the sound W would travel in some amount of time the speed of sound is dependent upon the properties of the medium one property would be the state of matter solids liquids versus gases we could assert that in general that the speed of sound within a solid is greater than that within a liquid and is greater than that within a gas for instance the speed of sound traveling through the solid aluminum is about 50 100 m/s but the SE speed of sound traveling through the liquid water is about 1,400 or500 m/s and for sound traveling through the gas air it's about 340 or 350 m/ second when it comes to a sound wave traveling through air the main property that affects its speed would be the temperature and we could write an equation that expresses the speed of sound in ear as a function of temperature it would look something like this the speed of sound is 331.65 * the temperature in degrees C if we were to substitute 20° into this equation we would get about 343.50 m/s the speed of sound is not dependent upon the frequency wavelength or amplitude of the sound wave and fully dependent upon the properties of the medium for any type of wave there is a mathematical relationship between the wave speed the frequency and the wavelength is given by this equation V equal F time Lambda the speed of a wave is dependent upon the properties of the medium and thenone affected by variations in the frequency wavelength or amplitude so for a way traveling through a uniform medium we could say that the left side of this equation is a constant value in a variation of the frequency would not affect the speed but instead would affect the wavelength length for instance a doubling of the frequency would cause the wavelength to increase by a factor of two while the speed remains constant and a tripling of the frequency would cause the wavelength to decrease by a factor of three while the speed remains constant and finally a haling of the frequency would cause the wavelength to increase by a factor two while keeping the speed constant the frequency and wavelength are inversely related while the speed is constant within a uniform medium at this time in every video that i' like to help you out with an action plan a series of nextx steps for making the learning stick but before I help you out could you help us out by giving us a like subscribing to the channel or leaving a question or comment in the comment section below now for your action plan here are three resources you'll find on our website and I've left links to each in the description section of this video you have a mindsone physics mission on sound properties that would be perfect followup for this lesson and you have a concept Builder and finally there's a tutorial page that's great for brushing up on the topic whatever you do I wish you the best of luck I'm Mr H and I thank you for watching