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Surfing the Web - An Introduction to Sound, Frequency, and the Acoustic Spectrum

Good day.

We think that people should be aware of this, so, here.

Link: https://www.prosaris.ca/post/introduction-to-sound

Link (Archive): https://webarchive.io/archive/5Ewq/https://www.prosaris.ca/post/introduction-to-sound/

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AI Summary:

The page gives a clear, structured introduction to what sound is, how we perceive it, and how different frequency ranges form the acoustic spectrum. Here are the main points, with precise citations to the sections you’re viewing.

🌀 What Sound Is

  • Sound is created by vibrating objects, which move surrounding air molecules and generate pressure waves we perceive as sound .

  • Air molecules do not travel with the wave; they oscillate around a rest point and return to it .

🔄 The Three Stages of Sound Creation

  1. Source vibration

  2. Wave propagation through a medium

  3. Biological detection by the ear

Sound waves enter the ear, vibrate the eardrum, and are converted into electrical signals interpreted by the brain .

📏 Frequency & Pitch

  • Frequency = number of pressure oscillations per second (measured in Hertz) .

  • Frequency determines pitch: low frequency = low pitch; high frequency = high pitch .

🔊 Decibels & Amplitude

  • Decibels (dB) measure sound intensity/loudness, not pitch or frequency .

  • Loud sounds above 90 dB can damage hearing with long-term exposure .

🌈 The Acoustic Spectrum

The full range of mechanical sound vibrations includes four major bands:

  • Infrasound: < 20 Hz — felt physically, not heard (e.g., volcano rumble)

  • Audible sound: 20 Hz–20 kHz — human hearing range (voices, music)

  • Ultrasound: > 20 kHz — used in mechanical/electrical diagnostics and animal echolocation

  • Hypersound: ~10¹³ Hz — beyond classical acoustic theory

⚠️ Effects of Non‑Audible Sound

Even sounds we cannot hear still produce decibels:

  • Infrasound may cause anxiety or nausea .

  • Ultrasound can cause headaches, dizziness, or ear pressure at high amplitudes .

  • Extremely high‑amplitude ultrasound (~180 dB) can cause severe internal organ damage without being heard .

🦇 Species Differences

  • Humans hear 20 Hz–20 kHz, but bats hear ~1 kHz to >200 kHz, meaning they audibly perceive ultrasonic frequencies we cannot .

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Important reading: 

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We hope that helps.

Keep the Faith. Best regards,

- The BMS Co., NDSMD

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