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Intensity, Intensity Level , and Intensity Spectrum Level

Intensity, Intensity Level , and Intensity Spectrum Level. The spectrum level is the intensity level of the sound wave within a 1 Hz band. band pass filter #1. hydrophone. band pass filter #2. Output. band pass filter #3. acoustic pressure. A Sonar System. band level. band #2.

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Intensity, Intensity Level , and Intensity Spectrum Level

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  1. Intensity, Intensity Level, and Intensity Spectrum Level The spectrum level is the intensity level of the sound wave within a 1 Hz band.

  2. band pass filter #1 hydrophone band pass filter #2 Output band pass filter #3 acoustic pressure A Sonar System

  3. band level band #2 band #3 band #1 frequency System Output • Fourier Transform of the Time Domain Signal • Frequency Analyzer

  4. Example

  5. 5 Pressure (Pa) 4 3 2 1 f (Hz) 330 440 220 110 Fourier Coefficients

  6. ISL ISLave f2 f1 frequency Band Level The Band Level is the intensity level over a band other than 1 Hz.

  7. 60 Intensity Spectrum Level (dB) 50 30 355 200 282 100 frequency (Hz) Example • Using the plot of ISL as a function of frequency shown, calculate • the band level of every band • the total band level • the total band level in a band from 150 Hz to 300 Hz

  8. tonals Spectrum Level broadband noise frequency Types of Spectrums

  9. Example What is the total BL?

  10. 60 Spectrum Level (dB) 50 30 355 200 282 100 frequency (Hz) fc=141 Common Bandwidths • Constant Bandwidth Df = constant • Proportional Bandwidth • Octave Bandwidth • f2 = 21 f1 • Half Octave Bandwidth • f2 = 21/2 f1 • Center Frequency

  11. Preferred Octave Bands

  12. Why do we care? Source Level (SL) and Noise Level (NL) are both examples of Band Levels (BL) where the frequency band(s) are defined by the frequencies of our Sonar System

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