What am I measuring?

2 thoughts on “What am I measuring?”

1. Explanation:
   When measuring the SPL level of a room, the average measurement across the entire
   environment (that is, throughout the room) is used. This establishes a baseline measurement
   referred to as the noise floor average. However, because sound dissipates over distance, when
   measuring the SPL of a specific source, such as an air conditioning vent or fluorescent light
   fixture, the SPL is taken from a defined distance from the source (for example, SPL = 30dB at 1
   meter away from the vent).
   The primary method of controlling ambient noise and reverberation levels within the room is to
   use the appropriate wall, flooring, and ceiling building materials. All types of building material
   have ratings associated with them for the following three acoustic properties:
   Noise Reduction Coefficient (NRC): The NRC is a rating that represents the amount of sound
   energy absorbed upon striking a surface. An NRC of 0 indicates perfect reflection; an NRC of 1
   indicates perfect absorption. NRC generally pertains to sound within the room and, therefore,
   applies to wall, flooring, and ceiling surfaces. The target NRC for a TelePresence room is .60.
   Sound Transmission Class (STC): The STC is a rating that represents the amount of sound
   energy required to transfer through a surface or structure. An STC of 40 requires greater than 40
   decibels of sound energy to transfer through the structure. STC generally pertains to sound
   leaking into the room from adjacent rooms and corridors and, therefore, pertains to wall and
   ceiling surfaces and items such as doors and windows that can leak audio. The target STC for a
   TelePresence room is 60 for internal walls, doors, and windows and 90 for external walls, doors,
   and windows.
   Impact Insulation Class (IIC): The IIC is a rating similar to STC but pertains specifically to
   flooring surfaces. IIC measures the resistance to the transmission of impact noise such as
   footfall, chairs dragging, and dropped items. This measurement is especially important in
   multifloor buildings and with plenum flooring. The IIC represents the amount of sound energy
   required to transfer sound through a surface or structure. An IIC of 40 would require greater than
   40 decibels of sound energy to travel through a surface or structure. The target IIC for a
   TelePresence room is 60.
   Appropriate noise level is less than 45 dB of noise in the room

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2. answer B: SPL is correct

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