RCDD · Question #200
You are designing a restaurant located within a retail mall. The ambient noise level of the restaurant is 70 dB. The ambient noise level of the mall common space is 75 dB. What is the MINIMUM sound…
The correct answer is C. 80 dB. A paging system must exceed the local ambient noise level by at least 10 dB to achieve the minimum signal-to-noise ratio required for speech intelligibility.
Question
You are designing a restaurant located within a retail mall. The ambient noise level of the restaurant is 70 dB. The ambient noise level of the mall common space is 75 dB. What is the MINIMUM sound pressure level (SPL) that should be used when designing the paging system within the restaurant?
Options
- A70 dB
- B75 dB
- C80 dB
- D85 dB
How the community answered
(62 responses)- A16% (10)
- B6% (4)
- C73% (45)
- D5% (3)
Why each option
A paging system must exceed the local ambient noise level by at least 10 dB to achieve the minimum signal-to-noise ratio required for speech intelligibility.
70 dB matches the ambient exactly, producing a 0 dB SNR that renders paging speech completely masked by background noise.
75 dB provides only 5 dB SNR above the 70 dB restaurant ambient, which is below the 10 dB minimum threshold for intelligibility.
The operative ambient noise level inside the restaurant is 70 dB. Standard practice requires paging SPL to be a minimum of 10 dB above the local ambient to ensure intelligibility (minimum SNR of 10 dB). Therefore 70 + 10 = 80 dB is the minimum design target. The 75 dB mall figure describes an external environment and is not the reference for the interior paging calculation.
85 dB exceeds the 10 dB SNR requirement by 5 dB and is therefore above the minimum - the question asks for the minimum SPL, not a comfortable or preferred level.
Concept tested: Minimum paging SPL design based on ambient noise SNR
Source: https://www.avixa.org/training-certification/certification/cts
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