Understanding Sound Waves: Physics, Properties, and Digital Audio

Understanding Sound Waves

Sound is produced by the vibration of an object moving through an elastic medium. For humans, audible vibrations range from 20 Hz to 20,000 Hz.

Key Characteristics of Sound

• Amplitude: Determines the intensity or volume of a sound. Larger waves result in louder sounds, while smaller waves are softer.
• Pitch (Tone): Allows us to perceive sounds as acute (high) or serious (low).
• Timbre: Helps us distinguish between different voices or musical instruments.
• Infrasound: Frequencies below 20 Hz.
• Ultrasound: Frequencies above 20,000 Hz.

Wave Physics

• Period (T): The time taken to produce one complete cycle.
• Wavelength (λ): Calculated as λ = v / f, representing the distance a sound travels in one complete cycle.
• Frequency (f): The number of complete cycles per second, measured in Hertz (Hz).

Digital Audio Fundamentals

Analog data is converted to digital format through sampling. The standard for CD audio is defined by a sampling frequency of 44,100 Hz and a 16-bit resolution. Audacity is a free tool that allows users to record, play, and export audio files in formats such as WAV and OGG Vorbis.

Calculating Digital Audio Storage

To calculate the space needed to record a voice with a sampling frequency of 11 kHz, 8-bit resolution, and mono audio for 3 minutes:

• Sampling Frequency: 11 kHz = 11,000 Hz
• Resolution: 8 bits
• Channels: 1 (Mono)
• Time: 3 minutes × 60 seconds = 180 seconds
• Total Samples: 11,000 samples/sec × 180 seconds = 1,980,000 samples
• Bits per Channel: 1,980,000 samples × 8 bits = 15,840,000 bits
• Total Bits: 15,840,000 bits × 1 channel = 15,840,000 bits
• Total Size in Bytes: 15,840,000 bits / 8 bits = 1,980,000 bytes (approximately 2 MB)