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DC215 Basics of Sound
Transcript of DC215 Basics of Sound
• 344 meters/sec in air at 20°C
Basics of Sound
• The theory states that, in order to avoid unwanted
digital artifacts (aliasing) when recording audio,
you must use a sample rate that is double that of
the highest frequency recorded.
• Since we hear up to 20 kHz, we must use a sample
rate of at least 40 kHz.
• To make up for digital errors, among other things,
we generally start off with a sample rate of 44.1 kHz.
• NYQUIST THEOREM
• At 48kHz, for example, you’re getting 48,000
samples a second.
• You can think of this as thousands of audio snapshots
per second. The greater the number of snapshots,
the closer the digital audio sounds to the original
•The Sample Rate is the number of times your audio
is measured (sampled) per second.
• In other words, we perceive amplitude as loudness.
• The amplitude of a wave is closely related to how
loud it sounds.
• The range of human hearing is
20 Hz - 20,000 Hz (20 kHz)
• Just under 262 Hz = middle C
• For example, 110 cycles per second, or 110 Hz = a low A
• BIT DEPTH
• SAMPLE RATE
• Digital Audio is greatly affected by two factors:
• A 6dB increase results in a doubling
of perceived volume
• It expresses a ratio between two given amplitudes.
• The decibel (dB) is used to describe gains and losses
in signal power within an audio system.
• Frequency determines the pitch or the
highness or lowness of a sound.
• Frequency is measured in Hertz (Hz).
• Frequency is the number of complete wave
cycles (one compression and one rarefaction)
that occur in one second.
• Also referred to as cycles per second.
converted to nerve impulses in cochlea
amplified by bones
vibrates ear drum
• 16 bits gives us 65,536 possible levels. 24 bits gives
• Dynamic range, simply put, is the difference between
loud and soft sounds.
• The greater the bit depth, the greater the dynamic
• On a graph, the sample rate is a vertical
measurement and bit depth is a horizontal measurement.
refers to the measurement or sampling
of a sound wave’s amplitude.
• The wavelength of 60 Hz (a bass drum fundamental)
is about 19 feet.
• The wavelength of 1,000 Hz (1kHz) is about 1.1 ft.
• Wavelengths are measured in distance units, such
as inches or feet.
• Measure of the distance that sound will take to complete
a single cycle.
Point of rest
Speed of sound
• Type of medium
• travels better through liquids and solids
• can’t travel through a vacuum
• Temperature of medium
• travels faster at higher temps