HTM2045 Example Calculation - Private offices within a hospital
Airborne Sound Insulation
From Table 6 in section 3.26 of HTM 2045, the required Privacy Factor (PF) for private offices is PF80. The mechanical services noise criterion (B) for private offices is NR30 (see Table 3 in section 3.10 of HTM 2045). Therefore the required weighted apparent sound reduction index (R’w) of all partitions enclosing the office (walls,floors, and ceilings) is given by:
R’w = PF - B (from rearranging PF = R’w + B)
= 80 - 30
= 50dB
Where B is the mechanical services noise criterion from Table 3 in section 3.10 of HTM 2045
Hence the required site tested weighted apparent soundreduction index (R’w) of all the office partitions is R’w 50dB.
When voices are raised, the sound level in the source room can be increased by up to 20dB, and therefore, to achieve the same level of privacy, the following correction factors should be added to the PF of the adjacent (receiver) room:
| Voice effort | Voice Effort Correction Factor (C) |
| Raised | 5 |
| Shout | 10 |
| Scream | 20 |
Hence for a different voice effort, say a patient screaming (in a maternity ward for example), the required weighted apparent soundreduction index (R’w) of the dividing partition could be increased by 20dB. Therefore, where the private office in the example above is located next to a maternity ward, the R’w of the office wall becomes:
R’w = PF - B + C
= 80 - 30 + 20
= 70dB
Similar procedures should be adopted for other construction elements which may effect internal noise transfer, for example suspended floors and ceilings. The performance requirements here would be in terms of weighted suspended ceiling normalised level difference (Dnc,w)and weighted floor normalised level difference (Dnf,w). For design calculation purposes these parameters would be treated in exactly the same way as R'w.
Impact Sound Insulation
The impact sound insulation performance of the floors between occupied areas should be such that, when tested, the arithmetic mean of all results for L'nT,w does not exceed 61dB. Furthermore no individual value should exceed 65dB
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