noise measurement 5
1-If two sound sources have 5 dB difference (ex. 90 dB and 95 dB), how many times of sound power difference will have between these two sources? Hint: Lw = 10*log (W/W0)
2-According to OSHA, a standard threshold shift is a change in hearing threshold relative to the baseline audiogram of an average of ___ dB or more at ________________ Hz.
3-To reduce the number of workers in your HCP, you want to assess if a noisy machine can be relocated away from workstation. Before relocation, you measure the TWA at the workstation and its distance from the machine (the only noise source) are 89 dB and 6 ft. If you move the machine further away from the workstation by 4 ft (that is a total of 10 ft from workstation), what dB would you be expected at the workstation? Will this relocation allow you to exclude the workers at the workstation in the HCP?
4-Doubling distance from sound source will _______(increase or decrease) the sound level by _____dB. Decreasing distance from sound source by half will _______(increase or decrease) the sound level by _____dB.
5-If a sound level of 92 dB is obtained at 3 ft away from a machine, what the sound level would you expect to be if you are at 1.5 ft away from the machine? Assuming free-field, non-directional noise source.
6-What’s the wavelength range human ears can normally hear? Hint: use f = c / λ
7-Use your own words to explain why sound pressure is easier to be measured than sound power.
8-If you plan to relocate a speaker from the center of a wall to the top corner (vertex) of the room (three walls of 90 degree angle each). From the same distance to the speaker, will the sound level remain the same after relocation? Show your calculation and include appropriate unit.
9-(This is a tricky question!!!! Think twice before you give me your answer!) You conduct a noise survey and measure the dB at a workstation and its distance from the machine (the only noise source) are 89 dB and 6 ft. According to OSHA, should the workers at this workstation be included in you hearing conservation program? Why and/or why not? Give me the OSHA regulation.
10-To reduce sound intensity level by 9 dB, how many times of distance from reference sound source location need to be increased in a free field? Show the appropriate equation and your work process for full credit.
11-According to OSHA, audiometric tests must include the following minimum six test frequencies: _________________________
12-How will sound intensity change if tripling distance (d2 = 3*d1) from a sound source? Show your calculation.
13-If a sound level of 92 dB is obtained at 3 ft away from a machine, what the sound level would you expect to be at 6 ft away from the machine? Assuming free-field, non-directional noise source.
