Objective: To identify whether positive, negative, or zero work is being done, to identify the force that is doing the work, and to describe the energy transformation associated with such work.
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DeciBels, Phons, and Sones
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Use a table of source-intensity-deciBel data to answer questions regarding the deciBel scale.
Use equal loudness curves to determine the phon rating of a sound if given the deciBel rating and the frequency.
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Use the Sone scale to compare the relative loudness of two sounds.
The Phon Scale 2
Use the concept of the Phon scale to answer basic questions that pertain to its comparison with the deciBel scale.
The DeciBel Scale
The Sone Scale
The Phon Scale 1
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Decibels, Phons, and Sones
The rate at which sound energy reaches a given cross-sectional area is known as the sound intensity. There is a large range of intensities that humans can hear. Given the large range, it is common to express the sound intensity using a logarithmic scale known as the decibel scale. By measuring the intensity level of a given sound, the deciBel rating can be determined. Table 1 lists intensity values and decibel ratings for several sound sources.
Intensity values and deciBel levels (dB) are objective measures of a sound. On the other hand, the loudness of a sound is subjective. Sound loudness varies from person to person. Furthermore, sounds with equal intensities but different frequencies are perceived by the same person to have unequal loudness. For instance, a 60 dB sound with a frequency of 1000 Hz sounds louder than a 60 dB sound with a frequency of 500 Hz. The unit phon is used to indicate an individual’s perception of loudness. By definition, 1 phon is equivalent to 1 deciBel at 1000 Hz (1 kHz).
Figure 1 shows several experimentally-determined equal loudness curves. Volunteers were subjected to a 1 kHz sound at 60 dB; this is a loudness of 60 phon. Sounds with different frequencies were then played; the volunteer adjusted the decibel level until it was perceived to have the same loudness as it had at 1000 Hz. This was repeated for varying frequencies to generate the entire 60-phon curve. To create an 80-phon curve, subjects were exposed to 1 kHz sounds at 80 dB. For other frequencies, they adjusted the decibel level until it was perceived to be of equal loudness as the 1 kHz sound. Figure 1 represents an average of the results for many individuals .
The sone scale is a third scale associated with the loudness of a sound. According to the sone scale, a 1 sone sound is defined as a sound whose loudness is equal to 40 phons. A 10 phon increase in a sound level is most often perceived as a doubling of loudness and thus a doubling of the sone rating. Figure 2 is generated based on these assumptions.
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Template Version 1.2 Added Question Scene 4 for Table Completion