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Medical Physics

Sensitivity and frequency response

  • 4 things to know
  • Paper 3, section B

Overview

Sound intensity, the decibel and dBA scales, and equal loudness curves.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Numbers

What is sound intensity, and how does perception relate to the actual value?

Numbers

What unit is sound intensity in, and how is intensity level in decibels calculated?

Numbers

What does I₀ represent, what does each 10 dB step correspond to, and what is the intensity level of a 1.0 × 10⁻⁵ W m⁻² sound?

Numbers

How do the dB and dBA scales differ, and what does 0 dB correspond to?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What are equal loudness curves (Fletcher-Munson curves)?

    Model answer

    Plots showing the sound pressure level required at each frequency for a listener to perceive sounds as equally loud.

  2. 2

    At which frequency range is human hearing most sensitive, according to equal loudness curves?

    Model answer

    Around 2-4 kHz.

  3. 3

    How does human hearing sensitivity vary at low and very high frequencies compared to mid-range frequencies?

    Model answer

    Hearing is less sensitive at low and very high frequencies, requiring greater sound pressure levels to perceive the same loudness.

  4. 4

    How do equal loudness curves differ between low and high intensity levels?

    Model answer

    At low intensity levels, the curves show greater variation with frequency; at high intensity levels, the curves flatten and hearing sensitivity becomes more uniform across frequencies.

  5. 5

    Define the phon as a unit of loudness level.

    Model answer

    A sound has a loudness of n phons if it is perceived as equally loud as a 1 kHz tone at n decibels.

  6. 6

    How does human perception of sound intensity relate to actual intensity changes?

    Model answer

    Human perception is approximately logarithmic: a doubling of perceived loudness requires roughly a tenfold increase in intensity.

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