The sounds they are vibrations that propagate through a medium. For sound to exist, there must be some source (object or element) that generates them.
Sound does not propagate in a vacuum, but needs a physical medium: gaseous, liquid or solid, such as air or water, to propagate.
Depending on their intensity (acoustic power), sounds can be loud, for example: the blast of a cannon; or weak, for example: the hands of a clock. Loudness is the measure used to order sounds in a hierarchy from the loudest sound to the lowest.
Sounds are perceived by the human ear through the auditory apparatus that receives the sound waves and transmits the information to the brain. For the human ear to perceive a sound, it must exceed the auditory threshold (0 dB) and not reach the pain threshold (130 dB).
The audible spectrum varies from person to person and can undergo changes due to age or overexposure to very loud sounds. Above the audible spectrum are ultrasounds (frequencies above 20 kHz) and below, infrasound (frequencies below 20 Hz).
Sound characteristics
- Height. It is determined by the frequency of the vibration of the waves, that is, the number of times a vibration is repeated in a given period of time. According to this characteristic, sounds can be classified as bass, for example: when pressing with the fingertips the strings of a double bass and treble, for example: a whistle. The frequency of sounds is measured in hertz (Hz) which is the number of vibrations per second. Not to be confused with volume.
- Intensity or volume. Depending on their intensity, sounds can be loud or weak. It is possible to measure the intensity of a sound as a function of the wave amplitude (distance between the maximum value of the wave and the equilibrium point); the wider the wave, the greater the intensity of the sound (loud sound) and the smaller the wave, the lower the intensity of the sound (weak sound).
- Duration. It is the period of time in which the vibrations of a sound are maintained. This will depend on the persistence of the sound wave. Depending on their duration, the sounds can be long, for example: sound of a triangle (musical instrument) or short, for example: when slamming a door.
- Doorbell. It is the quality that allows one to differentiate one sound from another, since it provides information regarding the source that produces the sound. The timbre allows two sounds of equal height to be differentiated, this is because every frequency is accompanied by harmonics (sounds whose frequencies are whole multiples of the fundamental note). The amount and intensity of the harmonics determines the timbre. The amplitude and location of the first harmonics gives a certain timbre to each musical instrument, which allows them to be differentiated.
Examples of loud sounds
- An explosion
- The collapse of a wall
- The firing of a firearm
- The barking of a dog
- The engine of a car when starting
- The roar of a lion
- An airplane taking off
- The detonation of a bomb
- A hammer beating
- An earthquake
- A powered vacuum cleaner
- A church bell
- A stampede of animals
- A working blender
- Music at a party
- An ambulance siren
- A working drill
- A hammer breaks pavements
- The horn of a train
- A drummer
- The screams in a rostrum
- Speakers at a rock concert
- A motorcycle speeding up
- The waves of the sea crashing against the rocks
- A voice in a megaphone
- A helicopter
- Fireworks
Examples of weak sounds
- A man walking barefoot
- The meow of a cat
- Probing a mosquito
- The drops falling from the tap
- A working air conditioner
- Boiling water
- A light switch
- The rattle of a snake
- The leaves of a tree moving
- The vibration of a mobile phone
- The song of a bird
- Steps of a dog
- An animal drinking water
- A fan spinning
- A person’s breath
- Fingers on the keys of a computer
- The pencil on the sheet
- The jingle of keys clashing
- A glass resting on a table
- The rain watering the plants
- Drumming of the fingers of the hand on a table
- The refrigerator door closing
- A beating heart
- A ball bouncing in the grass
- Flapping of a butterfly