Acoustics

Where ever we are noise and we here sounds. A sound is arranged and pleasant where as noise is disorganised and chaotic. Sounds are defined “as elastic molecular fluctuations in the air or other media that create a chain reaction by putting the nearest particles in motion. The sound then will spread at a certain propagation velocity which is called the speed of sound in the medium in question.”Acouticics troldekt- YouTube

What this means is that when sound is created It moves thought the air colliding with nearby particles which then collide with the other creating a knock-on effect which allows you to here sound. This is why there is no sound in space because there are no particles in space for the vibrations to collide with. Space is a vacuum.

Sound pressure

Sounds pressure is measured in DB or decibels the higher the sounds pressure the higher the decibels. When you compare two different sounds they must be measured at equal distance because sound dissipates the further away the measurement. This very useful because when you mix something you get a visual representations of how loud a guitar is to a kick drum.

Vu meters

VU stands for volume unit meter is an audio metering device. This allows the user to measure the sound pressure or loudness of an audio signal. This was 1st used in the 1930s to help regulate transmissions over telephone lines. This over time was used and because more wildly used transfusing it self to be used by sound engineers. VU meters measure all channels giving an average sound level. This can show you a visual representation of sounds and also closely creates what a human ear hears.

The optimum audio level for hearing is generally around 0VU or 0Db.

Sounds basics

Sound is omnidirectional meaning that it travels in all directions away from the score, the number of sound waves a second determine the frequency of the sound. Frequency is measured in Hz and 1Hz= one vibrations per second. The human ear is especially sensitive the frequency and the audible hear range for a human is 20Hz- 20,000Hz. However over time humans are exposed to loud noises and the ear will determinate over time meaning that higher frequency s will be harder to hear when you get older and exposed to loud noises. Low bass waves have very few vibrations a second meaning that the frequency is low where as a treble sound has many vibrations a second meaning that the frequency is high. Here is a audio spectrum so that you can get an idea os where bass mids and treble are situated on a scale

a 20HZ wavelength in real life spans 17 meters long for a full rotation where as at 20,000 HZ the wavelength is 1.7 cm for a full rotation.

The volume of the sounds is determined by how big the wavelength is or the amplitude. Here is a diagram of how the air molecules are compressed by the sound giving an on-going effect displayed below.

One full compression and rarefaction makes full rotation. The best was to hear these compression and are rarefaction by using pitching forks.

Here is a compassion of air molecules about you can see that the sing wave is gigh about the line of incidence

Here is a rarefaction meaning that molecules are rare in this area you can see it is displayed about on the air molecule chart on the sign wave chart this dips below that line

When these make the compression and rarefactions and once mad will create a certain frequency.

Frequencies

When the pitching forks have made a cycle (a compression and rarefaction) this is what we call a frequency. Frequencies are measured in Hertz and the amount of Hz there is within one seconds determine is it is a high or low frequency.

Octaves are double the Hz. For example when you have a note, which is 440Hz the octave about that would be 880Hz. Here you can see that they have doubled in number. Reason why they are octaves is because they are just compression and refracting at double the rate so it would be a higher pitch but it would be of the same note just an octave higher.

Sound, which travels through different mediums

Sound travels though different mediums at different rates because there are more molecules in liquid that there are in air so that time to travels would be grated in the liquid because of the more molecules it would take to collide with one another allowing the sound to travel through that medium.

High frequency’s are ore easily absorbed that others because they have more move the same mass back and forth more times, which takes more energy out of the wave. Where as a bass wavelength penetrates easier because it has more

energy to move because the wavelength does have as much distance to travel that the treble wavelength.

Wave lengths are classified but bass mids and treble

Sub bass: 20-39 HzBass: 40- 99HzLow mids: 100-799 HzMids: 800-1999Hz Upper mids: 2000-9999 HzTreble: 10,000- 18000 Hz

Sounds travels at 344 meters a second no matter the frequency so there can be a delay for example if you are listening to a live band. In a case where this would happen they would situate speaker stands further away from the stage so that the audience would hear the same music at the same time as everyone else otherwise the crowd would be hearing two different parts of a song. Also the speaker stands provide more power are drive the music because especially open air conserts sound is easily lost because sound as Omni directional is will just fill out the space meaning that it can easily get lost.

How do we hear sound

Sound waves travel into the ear canal until they reach the tympanic membrane The tympanic membrane passes the vibrations through the middle ear bones these are called the malleus, the incus and the staple. After passing through here it travels to the inner ear is called the cochlea. Inside the cochlea, there are thousands of tiny hair cells. These hair cells change the vibrations into an electrical impulse which are transmitted to the brain vie the nerve connecting the brain to the cochlea.

Acoustics in the studio

A studio is specially designed for many reasons one being so you to maximum quality for you tracks and that nothing interferes with the sound you desire.

here you can see that the live room is not symmetrical because if it was it you would get frequencies which will just bounce off walls had stay in the room. Most ceilings are not flat to break up the sound so that it room sounds more neutral. Also the more cornets the better because it will again distribute the sound around the room making the room more acoustically treated. Also a recording studio is a room within a room so that it is sound treated and you don’t get any sounds leaking out of walls. Also you would notice in the computer room at the from towards the monitors it is acoustically very dead to the you can get your mix sounding good and it is not coloured sound. Also you would see that the studio is designed to be the best for the sound engineer. At the back of the studio room you would se that there is a 2nd focal point for other people eg the band. This usually is a bit more brighter sounding. This is because you can compare when listening is a usual room. Where as where the sound engineer sits it has to be dead because you do not want anything it alter the sound when mixing because when you transfer to other rooms it will not sound as good or very different than where you originally mix the track.