Revision as of 14:44, 19 May 2020

Page in Progress

Audio at Evergreen: Through Evergreens resources, students can use audio to improve most academic projects. Whether you want to set up a sound system for a presentation, record a song, interview, podcast, or gather sounds for a video, scientific analysis or computer program. See Media Loans Policies for more information on how to checkout gear and other resources.

Sound

Wave Elements

All sounds we hear are just air pressure variations hitting our ears at different rates. A speaker or piano radiates these variations, while a microphone captures the variations. If you hit a drum of pluck a guitar, it makes sounds because it is moving back and forth repeatedly. When moving out, it produces higher pressure for air particles to squeeze together and then when moving back, the surface creates low pressure for air particles to spread out. This process repeats until the energy put into the drum or guitar has been dissipated and it stops moving. The high and low pressure repeating is a wave.

• • show wave gif somehow

• Frequency: The rate of the wave is called the frequency. Frequency is measured in how many times a cycle of high then low pressure occurs per second. The cycles per second can be measured in hertz (Hz). If a guitar string vibrates 440 cycles per second, we would call that a frequency of 440Hz. That 440Hz note would be called an A note because of the frequency. We hear frequency as higher or lower pitches. A high pitch bird song will be a much higher frequency like 10,000Hz and a low pitched bass note could be 60Hz. Frequency is pretty synonymous with tone, note and pitch.

• Amplitude: The intensity of the wave is called the amplitude, we hear this as loudness and often describe it as volume. If you pluck the guitar string twice as hard and get the wave to oscillate back and forth twice as far, it has twice the amplitude and therefore we hear it as louder. Another common measurement of intensity is deciBels or dB. It is like an averaging of amplitudes over time.
• Phase: There is a third main element of a sound wave called phase. It is the time that the wave starts compared to other waves. It can be important to consider because sounds can be "out of phase" where their high and low pressure areas cancel each other out. If two microphone are picking up the same sound from differnt distance, they may have be offset and cause these kinds of cancelations.
  • show image of all 3 elements

Timbre

Timbre is pronounced "Tamber". Simply put, it is what the sound sounds like. This is what makes a 440Hz note (which is an A note) sound different when sung, played on a guitar or a violin. The timbre is influenced by two things, the partials and the envelope. Timbre can also be called texture, color and tone.

• Paritals: These are additional frquencies that occur when you play a note. Think of a guitar string playing that 440Hz note. That string actually produces many more frequencies in addition to that simple 440Hz frequency. In addition to the whole length of the string vibrating at 440Hz, the string is also vibrating halfway at twice the speed making it 880Hz. In addition, 1/3 of the string vibrates 3 times as fast being 1320Hz, and 1/4 vibrates at 4 times as fast being 1760Hz and so on. This process repeats infinitetely and all vibrations occur simultaneously creating a complex wave, that sounds rich. Each additional frquency is increasingly quieter, or in other words, lower amplitudes. We still call the note we played on guitar A because it has a fundamental frequency (the lowest frequency) of 440Hz while it has partials (all frequencies above the lowest) of 880Hz, 1320Hz, 1760Hz and so on. The way that harmonic partials occur in relationship to the fundamental frequency follows a mathematical concpet called the Harmonic Series which is the foundation for all musical harmony, expliaining why notes sound good together. You can tell the differnece between insturment because the amplitude of their paritals vary.
  • image of partials
• Envelope: Envelope is how the amplitude of a sound changes over time. It is how long the sound takes to get to its loudest point and then how long its takes to return to silence after the cause of the sound has stopped, like when a violinist takes the bow of the string or when the pianist releases the keys. Each instrument has a differnt envelope that affect its timbre.
  • image of envelope

Sounds in Spaces

We can hear the size and other qualities of a room based on how much reverb, delay and characteristics that become a part of the sound interacting with the space.

• Delay: Sound bounces off walls and floor spaces. This can cause the sound like the initial sound to hit your ears, but as that sound radiates around the room, you will hear it again as it bounces off the wall and hits your ears after the initial instance. That sound can bounce back and forth hearing it multiple times as it gets quieter. Each delay sounds like an instance of the sound. How long it takes for you to hear the delay and how many times it happens tell you a lot about the room you are in.
• Reverb: This is different from delay because it sounds like a washed out version of the sound source. You will hear it as the sound itself then a tail of a jumbled up version of itself. This happens when a sound interacts with a space for it to bounce off many versions of it, bounce off of many angles of the room and get to your ear over a duration of time. Each room has its own reverb.
• Frequencies in Space: The different frequency of a sound interacts with a space differently. Lower frequency will pass through surface or objects, or get caught up in the corners. Higher frequencies on the other hand, bounce off surfaces or get absorbed by it. These qualities plus delay and reverb tell you a lot about a space without having to consciously think about it. To improve the acoustics of a room, you can often use bass traps, and acoustic paneling to break up the simplicity of a flat wall and corners.
• Direction: How do you know what direction a sound is coming from? Is it left, right, behind you? Your ears are spaced apart so you can hear when a sound hits your right ear first then the left slightly after. This allows you to know a sound is approximately some degrees to the right. The shape of your outer ear helps you know if sound is in front of or behind you by filtering out frequencies. Your brain has come to know the characteristics of how frequencies are removed when it goes through the back of your ear and it tells you that the sound is likely behind you. If a sound goes more to the left or right can be controlled in audio systems with a control called panning.

Audio Systems

Audio Concepts

• Signal Flow: Sound waves in the air can be turned into an electrical signal called an analog signal using a microphone, mixed with other signal using a mixer, then sent back out as a new physical sound waves using a speaker. No matter the size or complexity of the system, it is important to think of it in terms of signal flow. What order is the signal flowing through different cables and gear, and what is happening to the audio at each step? This line of thinking will help with quick adjustments and troubleshooting issues.
• Gain Staging: An important concept to know is Mic vs line level signal. Microphones output a very weak signal out their cables, so whatever it is connected to needs to use a "preamplifier" to amplify that signal to a level so that it can withstand going through circuits and being recorded. a Preamp brings a mic level up to line level which is about 1000x bigger to Line level. is this process you face the biggest decision of gain staging, for more info on that read the gain staging section below. You need to choose if your signal is mic or line level as it goes into the preamp that may be in a mixer or interface.
• Stereo field:xx

Audio System Components

There are categories used to identify audio gear, but many items combine elements from multiple categories. For example, a mixer may also act as an interface. It is important to be aware of these categories and that they may be combined depending on the gear.

• Microphone: All Microphones turn acoustic sound into analog signal. The easiest mic to use is the "dynamic" mic. You can just plug it in and it's ready to go. Another common type is called the "condenser" which needs to be powered to work. Depending on the mic it may need to be supplied by a battery or "phantom power" which is usually 48volts of electricity sent to the mic from whatever you are connecting it to like a mixer. There is often a button that says "48v" to enable it. You can do a lot with microphones and there is a great variety of them used for different purposes. If you want to know more about mics, check out the [Microphone WIKI].
  • image of sm57 and

• Cable: For most uses, cables are straight forward, you find the cable with a plug that connects to the socket you want to connect. The most common are XLR, 1/4", 1/8" (mini 3.5mm aux), and RCA. If you don't know what connector you need, you can look up your equipment make and model to find a manual with connector information. USB and other computer cables can carry digital audio signal if your gear is designed to utilize it. For advanced systems, you may want to learn the difference between balanced and unbalanced signal.
  • use images from caelin
• Interface: In audio an interface refers to an audio device which connects an analog system to a digital system. They are used to take the analog signal (voltage) from a mixer or microphone, and convert it to digital signal (1's and 0's). You can use USB to connect the interface to the computer to record the digital audio. Other gear can function as an audio interface because some have the ability to connect analog inputs to digital outputs that then go into the computer to be recorded. Media Loan has an interface called the "Black Jack". There is also a microphone that acts as an interface called "Blue Yeti". There are 2 kinds of analog mixers, and 2 field recorders that all have the ability to act as an interface.
• Mixer: A mixer is a type of equipment used to take in multiple audio signals "mix" them and send them to another part of the audio system like speakers, or a device to be recorded.MixerDifferent effects like Phase, panning, or bus Bus aux insert group
• Recorder: Anything that stores audio. A field recorder, like the "LS-100", is the most popular kind of recorder in Media Loan. But if you were to use an interface and record on a computer, that computer would be a recorder. Media Loan also has tape recorders.
• Amp: An amp is an amplifier, which takes an analog signal and makes increases the gain, which you can think of as volume. Guitar players call the speaker they connect their guitar to an amp, but it is actually both a speaker and an amp in one box. Some devices are just amps, and some devices are just speakers and they need to be connected. if your speaker has a fan in it, that is probably because it is cooling an amp. Most gear the receives microphones have a preamplifier, which is a kind of amp that makes a mic level turn in to line level, but that was discussed in the above gain staging section. Most amps, that aren't specifically preamplifier, convert line level to speaker level so it can have enough gain to be heard on a speaker
• Speaker: There are many different uses for speakers and each has their own type of speaker. Of course there are headphone and guitar amps. For events the bigs ones facing an audience are often called mains, or house. If you have any facing the performers so they can hear themselves they are called stage monitors. We also call speakers used in recording studios monitors because you are monitoring the mix.
• Support: This term isn't an audio industry term, but rather how Media Loan categorizes items that hold audio gear. These kinds of gear can be overlooked, but are very helpful to getting clean audio. Media Loan has mic stands, speaker stands, pistol grips, boom poles, gorilla pods, goosenecks, stereo mount adapters.

Recording

Space

• studio
• feild
• computer
• Interface
• quiet room, eliminate noise

Digital audio

• , representation of a waveform, adc dacbinary

• Concept of a digital audio fileFiles on computer
• To record digitally, the analog signal from a microphone is reduced to 1's and 0's in a computer to represent "samples". Samples can be thought of as the smallest digital unit of a digital recording, it represents
• Talk about examples of file types we are familiar with like mp3, cd, records, tape
• Sampling
• Artifacts

Daw

• Using a Daw, Link to daw foldersThey are all pretty similar

• Midi
• Sequencing layering

Effects

• Pluginseffects

• have talked aboutReverbPhase panning
• havent Compression, EQ
• Left to right
• eliminate noise, attachments

Public Address

Safety

• Don't press buttons randomly or plug in gear, be conscious of raised up trims and gains
• Gaff dow cables so attendees don't trip on your cables,

Feedback

• Eq for feedback
• Eq for audio quality

setting up

• Mic vs lineTest output with music from an ipod
• Mic check
• mono
• Headphones, solo butto

• Where to set up
  • Listen from where the audience will be and have a person operate the mixer during the performance if needed.
  • ML gear can only accommodate a x mic input performance.

• Diffeent set ups
  • Little mackie
  • Bigger stereo speakers
  • With monitors for