Acoustics and Audio Technology: Key Concepts Explained
Acoustics and Audio Technology
Reflection: A sound wave reflects at an angle equal to the incident angle, influenced by the material’s absorption. Refraction: This is the change in direction of a sound wave. Diffraction: Occurs when a sound wave encounters an obstacle in its path. Interference: The effects that occur when sounds from various sources interact with the direct wave. Sound Absorption: Happens when a direct wave hits a surface, reflecting a new wave with lower amplitude. Resonance: When a material vibrates at its dominant frequency after a sharp impact, it is quickly damped.
Audio Equipment and Signal Processing
Unbalanced Lines: Commonly used in home audio and semi-professional equipment, using one path for the signal and another for return. Balanced Lines: More effectively reject interference than unbalanced lines. Phantom Power: Uses symmetrical drivers to carry the audio signal to power microphones. Impedance: Indicates the load a speaker presents to an amplifier at a specific frequency. Resonance Frequency: The characteristic frequency of a diaphragm’s mechanical vibration. Crossover Filter: Separates the audio spectrum, directing frequencies to the appropriate speakers using low-pass, high-pass, and band-pass filters.
Preamplifiers and Signal Adaptation
Preamplifier: Selects, amplifies, and controls signals from various sources (analog or digital) to drive the power amplifier. Input Selector: Adapts the amplifier input to the characteristics of the selected signal source. Impedance Adapter: Adjusts input impedance and level to provide a suitable signal to the main preamplifier. RIAA Preamplifier: Amplifies and equalizes the phono input signal, correcting for recording effects.
Amplifiers and Signal Amplification
Amplifier: Increases the signal at its input to a power level sufficient to move speaker cones. Signal to Noise Ratio: The relationship between the desired audio signal and the undesired residual noise. RIAA Amplifier: Enhances low frequencies and attenuates high frequencies to convert recorded information back to the original sound. Power Amplifier: Amplifies the preamplifier’s signal to a level of tens of watts to drive speakers.
Amplifier Classes
Class A Amplifier: High and constant power consumption, regardless of the audio signal. Class B Amplifier: No current flows through the output transistors until an audio signal is applied. Class AB Amplifier: Output current flows for more than half but less than a full period of the input signal. Darlington Amplifier: Two transistors in emitter follower configuration, characterized by high current gain, high input impedance, low output impedance, and voltage gain close to unity.