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Created: 5/12/2020
Introduction
Introduction
Acoustic engineering is generally related to the generation, transmission, and reception of audio, as well as its effects on human hearing. These effects are conveyed through mechanical waves propagating in physical mediums such as air and liquid. A key point to remember is that the perception of loudness is subjective and unique to each individual.
Background
Background
Decibels
Decibels measure the relative difference between a signal and a reference. Due to the large dynamic range of human hearing, a logarithmic scale (dB) is effective for quantifying large variations.
Sound Pressure level (SPL)
This is a measure of the loudness of sound as experienced by the human ear, quantified in terms of sound pressure amplitude in decibels.
Weighting Curves
Generally, there are several weighting curves, with A and C being the most commonly used.
Audio Range
The standard hearing frequency range for humans is between 20 Hz and 20 kHz. .
Spectrogram:
This is a time-varying graphical visualization of SPL levels relative to the frequency spectrum.
In the plot, the x-axis represents time in seconds, the y-axis represents frequency in Hz (on a logarithmic scale), and the color intensity represents the signal intensity in decibels (dB).
See a real spectogram here: https://en.wikipedia.org/wiki/Acoustics#/media/File:Oh_No_Girl_Spectrogram_2.jpg
Detailed Explanation
Detailed Explanation
Audio Generation
This involves an electroacoustic transducer, such as a speaker driver, which can be a full-range, subwoofer, woofer, or tweeter, each covering a different range of the audio frequency band.
Audio Transmission
This process involves wave propagation. In the far-field region of the wave, the SPL level typically degrades by 6 dB for every doubling of the distance from the source in an anechoic chamber.
Room Acoustics
In practice, rooms are reflective and echoic, causing the rate of loudness level degradation with distance to flatten out within a few meters.
Audio Reception
This involves converting sound waves back to electric voltage using an electroacoustic transducer, such as a microphone.
Q&A
Q&A
How do sound levels add?
Convert to a linear scale using the anti-log.
Add or subtract the levels.
Log the results back.
For example, two 60 dB noise signals would add up to 63 dB.
Summary & Conclusion
Summary & Conclusion
Acoustics is the study of the generation, propagation, and reception of pressure waves and their effects on hearing
Acoustic transducers transform pressure waves to electric voltage and vice versa
The human hearing range is generally 20 Hz to 20 kHz.
Further Reading and Practice:
Further Reading and Practice:
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