Sound

What is sound?

Sound is a wave that is created by vibrations, which travels through mediums. These could be anything from a gas (like air) to a liquid (like water) or even a solid (like a wall.) Therefore, sound can't travel in space, because there is nothing but a vacuum which has no particles.When sound vibrations pass through something, the particles inside get a push and then a pull (also known as an oscillation), like in a slinky. This is the equilibrium position. Sound waves are longitudinal waves, which means that the waves are along the same direction that it travels. This is what makes them different from transverse waves, which are waves that have the vibrations at right angles to the direction it travels. Examples of transverse waves include light and water waves.

Tuning Forks:Tuning forks are a good example of showing how sound travels. When you bang the fork on something, the ends of it vibrate, in turn vibrating (oscillating) the air particles around it. You can hear the sound better when you put the fork down on a solid surface, because the particles are closer and more packed together in a solid and the sound passes through faster.

The measurement of sound:

Loudness:Loudness, also known as amplitude, is measured in decibels (dB). Unlike linear scales like that of a thermometer, when the numbers change the same amount from 10-20 or 20-30, etc., decibels work quite differently. For every increase of 10dB, this equals a doubling in intensity. (i.e: 10dB to 20dB means that 20dB is twice as loud as 10dB.) The louder a sound is, the more energy it transfers (sound is a form of energy, as well.) The human threshold of hearing ranges from 10dB, but the pain threshold is at 120dB.Damage:Because louder sounds have more energy, they make the eardrum vibrate with more energy, which results in bigger vibrations. When this goes on for a long-term interval, it damages the eardrum, and could potentially make someone deaf.

Pitch and Volume:

Loudness = Amplitude = Size of VibrationsFrequency = Pitch = Waves Per SecondPitch:Pitch (also known as frequency)is how high or low a note is on a musical scale. A note's pitch doesn't change, but its volume can. On an oscilloscope, the pitch can be read by how wide the waves are. For instance, if the wavelength is shorter, that means there are more waves per second and the note is higher; likewise, if the wavelength is longer, there are less waves per second and the note is lower.Loudness:Loudness (also known as amplitude) is the intensity of a sound - this is linked to the source of the sound. On an oscilloscope, the loudness of the sound can be read based on its height. If the height of the waves is taller, that means the sound is loud, but if the height is shorter, then the sound is quieter.

Measuring Frequency:Pitch is measured in Hertz (Hz), and is represented as 1Hz = 1 wave per second. Humans can hear sounds between about 20Hz and 20kHz (20,000Hz). However, as humans grow older the range decreases, so adults can't hear as high frequencies as children.

Echoes:

Echoes are sound waves that are reflected when they bounce off a surface. They occur more on smooth, hard and flat surfaces, but soft and textured surfaces absorb the sound more rather than echoing it. An example of this is curtains and soft furniture.Because sound is a wave, it also obeys the laws of reflection, including that the angle of incidence = angle of reflection.Speed of Sound: In air, sound travels at 300 m/s. In water, it travels at 1500 m/s. In various solids, it travels at several thousand metres per second. Sound travels faster in solids because the particles are closer together so the vibrations pass through quicker.Ultrasound:Ultrasound uses sounds that are too high pitched for humans to hear and is most commonly known for being used for pre-natal scans. this works by sending the waves out and timing the echoes to build up an image of the embryo.

Musical Instruments:

Stringed Instruments:In stringed instruments the pitch of the notes played depends on three factors: the length of the string: the longer the string, the lower the note the thickness of the string: the thicker the string, the lower the note the tension on the string. the looser the string, the lower the note Size applies to all instruments as well; the larger the instrument, the deeper and lower a sound it makes.Woodwind Instruments:The pitch depends on: how hard/soft you blow on the reed which holes you cover with your fingers Brass Instruments:In a brass instrument, the pitch depends on: (trombone) how tight it is (when you push/pull the slide) how hard you blow on the mouthpiece Percussion:The pitch depends on: how tight the skin on the drums is (steel drums) how near the centre you play

Parts of the Ear:

Sound is transmitted to the nerves when the sound waves hit the eardrum. This makes it vibrate and pass on the vibrations to the cochlea, which in turn passes them on to the auditory nerves to the brain.