What is sound? Sound is the vibrating of air molecules under pressure. There are tens of thousands of different frequencies, or pitches, in the range of between 20 and 20,000 hertz (Hz).
The human ear can hear a frequency up to 20,000 hertz.
In contrast, animals such as bats and dolphins can hear higher frequencies than humans.
One of the most important things about sound is that it travels through space. If a sound source (a person’s voice for example) is too far away from your ears, you can’t hear it. For example if you are standing inside a room with windows on all sides, then outside you can see the sun shining out but inside there isn’t any light at all because your ears are so far away from the source that there isn’t any sound coming from it at all.
Sound waves travel from their source (a voice or other source) to your ears through air molecules and then into your body by way of tiny hairs that grow on the skin and in the ear canal. The pressure changes as they pass through these tiny channels in your ear canal are measured using a device called an electrocardiogram or ECG, or an electroencephalogram (EEG) which measures electrical activity in the brain stem (the part of your brain responsible for basic functions such as breathing, heartbeat and balance).
Sound is measurable. It’s measured as a change in pressure when sound waves reach the ear or a measuring device. Sound exposure is usually measured in decibels of sound pressure level (dB SPL), which is a measure of the sound pressure level relative to the lowest hearing threshold of the young, healthy ear set at 128dbH.
If you had to guess, how loud does it need to be for you to hear? Is it enough for you to easily hear a TV show? Are you deaf if your ears are blocked by a bag? How loud was it when you were shopping at Nordstrom last week? How quiet was it when you were sitting in silence on your couch watching Netflix? The answer is not always clear.
The reason why can vary from person to person depending on where they live and what their work environment is like. In some cases, people may have more sensitive hearing than others even though any given level may actually be about 10db lower than what many would consider “loud”.
Your ability to hear depends on three factors:
1) the frequency range of sound
2) the size and shape of your ears and
3) how much air moves through them while they are in motion.
All three factors make up the auditory spectrum, which ranges from low frequency tones (so-called “white noise”) to high frequency tones (like music). Audio frequencies travel through air at different speeds depending on its density and temperature. The higher the number (the higher speed), the less air passes through it; consequently, low frequencies travel more quickly than high frequencies do.
Bottom line: If your ears are closed by a bag that blocks out all sounds but white noise; if your ears are closed by an earplug that blocks out all sounds but music or if your ears are totally blocked by dust in your pocket – no matter what type of ear blockage there is – you will not hear any sounds.
The Decibel Scale
The decibel scale is a method of measuring sound pressure levels. It is also known as the sound-measuring scale because it was developed to measure the amount of sound that reaches a person’s ear.
The decibel scale is based on the relationship between the pressure of sound waves and the volume of air molecules. The higher a sound wave’s pressure, the greater its volume. For example, if you were to stand in a 1m diameter circle with your finger pointed at 2 meters away, you would experience a 2dB SPL (and would feel it too) when that finger was at 2 m away from you.
But when your finger was at 2m away from you, your finger would experience a 4dB SPL .Sound levels can vary with distance from an object such as when an object is close or far from another object or when an object is moving relative to another object.
This variation in relative distance and direction can cause apparent differences in intensity between audible and subaudible frequencies; hence, decibels refer to dB SPL rather than magnitude (pointing directly towards you) or absolute intensity (pointing directly away from you).
A reduction in relative distance due to movement may be expressed as an increase in perceived loudness provided those changes are perceived by all objects falling within the same location.
For example, if an object were 5 metres away from another object that was 5 metres away from it, we would perceive both objects as substantially louder (more intense) than they actually were (because we perceive them as being approximately equal in intensity).
Threshold of Hearing and Pain Level
Threshold of hearing (TOH) is the upper point at which a sound becomes audible to the human ear. A TOH of 85 dB is a threshold of hearing, while an 80 dB TOH is above average and a 70 dB TOH is above average for the human ear.
The ability to hear sounds below 85dB SPL depend on the age, gender and size of the listener. In addition, there are conditions associated with hearing loss that may cause temporary hearing loss such as tinnitus, conductive hearing loss and auditory nerve injury.
Most people are able to hear sounds above 80dB SPL at an age between twenty-five and forty-five years old; however, after this age, it takes longer for people to get used to loud noises because their ears have not adjusted.
There are many factors that can affect your perception of sound: age, gender and size/structure of the eardrum all play a role in how your ears hear sound; also there is an increase in inner ear pressure with aging that can affect how much air moves through them so they act as filters when exposed to noise.
This can cause temporary ringing in the ears or damage that permanently affects how well you can hear noise.
Sound is measured in three ways:
1. Acoustic measurements are generally made by engineers and technicians who have advanced training in the use of sound measuring instruments, including microphones, sound meters, and hydrophones
2. Thermal measurements are typically made by scientists and industrial engineers who have learned to measure sound by monitoring the temperature of a material
3. Electrical measurements are often performed by audio engineers who have learned to use electronic measuring devices such as an oscilloscope to evaluate sound levels.
Decibels (db) is a unit of measurement used to rate the intensity of sounds that humans can hear. The decibel (dB) is a logarithmic scale used to compare the loudness of different sounds.