# Pitch and Volume in Sound Waves – Video & Lesson Transcript

## Amplitude in Sound Waves

Plucking a guitar string creates longitudinal waves in the air, which produce sound.

Let ‘s start by recalling a few things about sound waves. While sound can travel through all types of substances, we ‘re going to use vent as the medium in our examples here. A bang-up way to visualize longitudinal waves in air travel is to think of the legal coming from a guitar string. When you pluck the string, it vibrates from side to side, pushing the surrounding air molecules in a periodic fashion. The compressions and rarefactions in the air comprise a longitudinal brandish, which we detect as sound. If we could look at just one air particle, we would see it oscillating back and forth. Sometimes the particles move back and forth over a very large distance. other times, the particles oscillate good a little ways. The total of cycle in the particles of the medium is related to the amount of energy carried by the curl. Can you remember which of the five wave parameters describes a wave ‘s energy ? And by wave parameters, I mean the frequency, wavelength, period, speed, and amplitude. One that describes a wave ‘s energy is the amplitude. In a cross wave, the amplitude can be seen as the altitude of the crests. But in a longitudinal wave, like voice, amplitude is a measure of how far the particles oscillate bet on and forth. In a high-energy roll, the amplitude is large, because the particles oscillate over a large distance. A low-energy roll has gloomy amplitude because the oscillations are minor in size. thus, now we get the kinship between energy and amplitude. But, how does that translate into what we hear as a legal wave ?

## Intensity and Volume

The decibel scale measures the intensity of sound waves.

The energy in a sound wave has to travel over a certain area in a certain amount of clock. We detect sounds as being brassy when we ‘re standing closer to the reservoir and quiet when we ‘re standing far aside. The amount of energy we detect is known as the intensity. Intensity is measured in units of energy over the area and time. In other words, it ‘s the sum of energy that is carried over a certain area in a certain total of prison term. We describe different levels of saturation using the decibel scale, a logarithmic scale for measuring the intensity of sound waves. normal conversation broadly falls around 60 decibels. A whisper is more like 20 decibels, while a vacuum cleaner runs a brassy as 80 decibels. You may be more familiar with decibels as a measurement of volume. When talking about sound waves, the volume is the perception of flashiness from the volume of a sound roll. The higher the intensity of a sound, the loud it is perceived in our ears, and the higher volume it has. Since volume is a function of energy, and energy is related to amplitude, then we can make the conclusion that the volume of a sound is proportional to the amplitude of the sound wave .

## Frequency in Sound Waves

It was a small bad trying to visualize the amplitude of sound waves. Because sound is a longitudinal beckon, we do n’t get the decent ‘up and down ‘ wave condition that makes it so easy to see the parameters. We figured out a way to see the amplitude of sound. But, what about the period and frequency ? Is there a way to see the parameters that are related to fourth dimension ? Let ‘s say a sound wave is traveling toward a microphone. The microphone picks up compressions and rarefactions as the brandish passes by. When a compression hits the microphone, it receives a high amount of vent atmospheric pressure from the particles in that space. During a rarefaction, the air blackmail is identical low. Over time, the microphone experiences ups and downs in pressure, which we can illustrate as an ‘up-and-down ‘ brandish like this :

The up-and-down wave shows the changes in air pressure that the microphone receives.

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It looks like a cross beckon, does n’t it ? But, it ‘s very a plot of pressure over prison term, showing us the periods between consecutive compressions of the wave. If we take the multiplicative inverse of the period, we can find the frequency. This fathom wave has a frequency of 262 Hertz. indeed, what does it mean when we describe waves as having a certain Hertz ? certain, we know it refers to the frequency of the wave. A wave of 262 Hz has 262 wave cycles passing by every second. A wave of 440 Hz has 440 cycles a second gear. But, what does that beggarly for a voice wave ? Can we hear the dispute in frequencies between two sounds ?

## Pitch and the Acoustic Range

Let ‘s go back to those two sounds we heard in the beginning. The note played here ( please see 05:13 in the video above ) has a frequency of 262 Hz. And, this tone here ( please see 05:19 in the video recording above ) has a frequency of 440 Hz. The first one was a Middle C, and the second was the A above Middle C, or Concert A. In music, the pitch of a certain note is defined as the perception of frequency. Hearing musical pitch helps us to put unlike sounds in order from gamey to depleted frequency. high-pitched notes have a gamey frequency, while low-pitched notes have a gloomy frequency. The difference in gear between Middle C and Concert A is a difference of 178 Hz .

The acoustic range represents the sounds that humans can hear.

Humans can typically hear sounds deoxyadenosine monophosphate moo as 20 Hz and adenine gamey as 20,000 Hz. This range is known as the acoustic range of good. Sounds above 20,000 Hz are considered ultrasound. Dogs, dolphins, and bats can hear sounds in the supersonic rate. At the other end of the spectrum is the range of infrasound. These are sounds that are excessively first gear for us to hear, like the communication calls between whales and elephants. obviously, we humans only play our music within the acoustic scope of heavy, between 20 and 20,000 Hz. When you ‘re able to discern a remainder between musical pitches, just know that what you very perceive is a difference in the sound waves ‘ frequencies.

## Lesson Summary

Sound waves are longitudinal waves that require a metier in which to travel. The medium consists of particles that oscillate within a certain amplitude. The amplitude of a voice roll is a reflection of how much department of energy is carried, which contributes to the intensity of the sound. Intensity is measured in decibels and is perceived as sound volume. Thus, the bulk is proportional to the amplitude of the sound beckon. The frequency of a sound wave is perceived as pitch. Humans can detect pitches within the acoustic range of 20 to 20,000 Hz, but we ca n’t detect ultrasound or infrasound. We can hear changes in frequencies of musical notes, which we describe as being changes in pitch. When we hear sounds, we describe them based on the pitches and volumes that we perceive. These entities are plainly our perceptions of the frequencies and amplitudes of phone waves .

## Learning Outcome

After watching this video recording, you will be able to :

• Describe the characteristics of sound waves
• Define several terms related to sound: amplitude, intensity and volume
• Explain how frequency is related to pitch
• Summarize what is meant by the acoustic range for humans