Study Notes on Sound and Audio Engineering

Definition: Sound is a vibration that typically propagates as an audible wave of pressure through a transmission medium such as a gas, liquid, or solid.

Role of Sound Engineers:
- Sound engineers are professionals who focus on the technical aspects of sound and music production.
- Their responsibilities include mixing, reproducing, and manipulating the equalization and electronic effects of sound.
- Sound engineers can work outside of the music industry, such as designing and controlling sound for events like conferences and in venues like theaters.

Monitor Sound Engineers:
- They manage the sound that the band hears on stage through monitors.
- Example: When a band member requests to adjust the sound levels of their instrument, they are speaking to the monitor sound engineer.
Systems Engineers:
- Responsible for setting up amplifiers, complex PA systems, and speakers for the band and other sound engineers.
Studio Sound Engineers:
- Work in recording studios to create high-quality recordings of music, speech, and sound effects.
Research and Development Audio Engineers:
- Focus on inventing new technologies, equipment, and techniques to enhance audio engineering processes and art.
Wireless Microphone Engineers:
- Deal with wireless microphones during theatre productions, sports events, or corporate events.
Game Audio Designer Engineers:
- Specialize in sound for video and computer game development.

Pitch:
- The quality of sound governed by the rate of vibrations producing it; defines the highness or lowness of a tone.
Tone:
- Refers to the kind of sound in a musical note or a person's voice, which can express various emotions depending on context (e.g., a poem vs. a newspaper article).

Definition of Audio:
- Audio refers to sound within the acoustic range available to humans.
Audio Frequency (AF):
- An electrical alternating current within the range of 20 to 20,000 hertz (cycles per second) used to produce acoustic sound.
Computer Audio:
- The sound systems integrated into or added to computers.

Function:
- An audio card contains a built-in processor and memory for audio file processing, which sends audio signals to speakers in the computer.
Digital Conversion:
- Sound, in sequence of analog signals, is converted to digital signals using an analog-to-digital converter (ADC), allowing it to be played back.

Compression:
- Audio files are often compressed for storage or faster transmission.
File Formats:
- Common formats include Wave file format and the MP3 (MPEG-1 Audio Layer-3) format, which is the most popular today.
Streaming Sound:
- Audio must be delivered as streaming sound for real-time listening, like in multimedia presentations or online conferences.

Enhancing Multimedia:
- Audio enhances web lectures, adds emotion to presentations, and incorporates non-speech audio for user interfaces.
Advantages of Using Audio:
- Provides an interface for visually disabled users.
- Offers additional information, supporting various learning styles.
- Adds realism and cultural context, subject to cultural interpretation.
- Directs attention to events with non-speech audio signals (e.g., an error sound).
- Increases engagement and eases communication, as users may prefer spoken word over text.

Definition:
- The range of signals audible to the human ear, defined in Hertz (Hz).
Units of Frequency:
- Hertz (Hz): one cycle per second
- Kilohertz (kHz): $10^3$ Hz
- Megahertz (MHz): $10^6$ Hz
- Gigahertz (GHz): $10^9$ Hz

Decibel (dB):
- The unit measuring sound intensity; the scale accounts for human ear sensitivity.
- For context: the sound of a jet engine is approximately $1,000,000,000,000$ times more powerful than the faintest audible sound.
Noise Intensity Levels:
- 140 dB: Threshold for irreversible damage
- 130 dB: Dangerous, harmful sounds
- 90 dB: Harmfulness threshold
- 70 dB: Normal speaking voice
- 0 dB: Hearing threshold (whisper)

Speaker:
- Converts analog audio signals into air vibrations to produce audible sound.
- Historically shielded to avoid interference with CRT monitors; quality improved since the 1990s.
Microphone:
- Translates sound vibrations into electronic signals or records them.
Headphones:
- Allow private listening of audio without disturbing anyone nearby.
- Known as earphones or depending on style, earbuds.
Amplifier:
- An electronic device increasing the voltage, current, or power of a signal.
- Categories: weak-signal amplifiers and power amplifiers.

Used primarily in wireless receivers, audio tape players, and compact disc players.
Designed for amplifying extremely small input signals, with minimal internal noise.

Used in wireless transmitters and broadcasting; commonly employ bipolar transistors.
Vacuum tubes are also popular for musicians who prefer them for better fidelity.

Definition:
- A technical standard that describes a protocol, interface, and connectors for communication between electronic musical instruments, computers, and audio devices.
- A single MIDI link can carry up to sixteen channels of information, routed to separate devices.

Definition:
- Sound recording and reproduction involve inscribing and recreating sound waves (e.g., voice, music, sound effects).
Classes of Sound Recording Technologies:
- Analogue recording
- Digital recording

Acoustic Analogue Recording Process:
- Achieved using microphone diaphragms to detect pressure changes from acoustic waves, recorded mechanically, e.g., on phonograph records.
Magnetic Tape Recording:
- Uses microphone vibrations converted to variable electric currents, recorded by an electromagnet onto magnetic tape.

Phonautograph:
- Featured a cone-shaped horn and a sharp point that recorded sound vibrations onto coated paper.
Phonograph:
- Mechanical device for recording and reproducing sounds, also known as a gramophone in its later forms.
Gramophone:
- Played records with grooves that were amplified by a needle. Though now archaic, it was once a primary medium for recorded music.
Telegraphone:
- The first practical device for magnetic sound recording on a wire, capturing varying magnetic fields caused by sound.