Marlborough House
+44 (0)20 8784 5784
Upper Marlborough House
+44 (0)20 8784 5700
St Albans, Herts AL1 3UT
www.fabermaunsell.
com
Statement from Amanda Robinson, regarding acoustic checks undertaken on the 12th and 18th June 2004
Further to our site visit undertaken this morning to repeat the measurements of the west wing chillers following
works carried out by Powermaster, we provide the following summation.
1. Without the chillers operating, the noise levels within the office area on the fourth floor adjacent to the
plantroom were of the order of NR35 in their current condition (this noise is likely to reduce further once
carpets are installed). When the chillers were first turned on, the noise levels in the 4th floor office area
increased to NR 46, and the tonal noise noted previously (250Hz) was clearly audible. However, after the
chillers had operated for a period of time, the noise levels reduced to between NR40 – 45.
2. The chillers were turned off again, and the settings adjusted by Derry’s. The measurements were repeated,
and it was found that this time, the noise levels with all plant operating were NR36 – NR41.
3. It would appear that the chiller noise level varies upon its initial start-up, as it adjusts to accommodate the
load. However, once operating under the required conditions, the noise produced reduces, and the tonal
content at 250Hz is significantly reduced. Following the works carried out by Powermaster, there has clearly
been a significant reduction in the noise level associated with the operation of the chillers. However, it should
be ensured that the specific condition that is creating the noise on startup is suitably controlled.
4. On the basis of the measurements taken on the second startup of the chillers, the noise on the fourth floor
adjacent the plant areas achieves the internal noise requirement of NR38 within the space.
5. It was noted upon inspection of the plantroom areas that there are still gaps around elements such as beams,
pipework and at the head of the partition etc., which are required to be sealed airtight. It is understood from
your discussions at the meeting this morning that B&K have committed to undertaking this task.
Page:
1
Doc. 29B
C:\Documents and Settings\david.tinsley.DERRY-BS\Local Settings\Temporary Internet Files\OLK679\Chiller Acoustic Resultst_ar180604_memo on chiller repeat measures.doc
Building
Description
Comment
31.5 Hz 63 Hz 125 Hz 250 Hz 500 Hz 1.0 k
2.0 k
4.0 k
8.0 k
NR
Leq
East Wing
4th floor near plantroom
water noise from pipework
58.9
54.5
51.3
48.5
40.8
37
30.8
25.7
20.7
39
44.1
4th floor near plantroom
water noise from pipework
61.6
53.2
53.1
48.4
41
38.8
32.7
27.9
25.8
39
44.9
4th floor near door to atrium
54.5
49.1
45.7
41.9
36.6
36.9
34.4
25.2
18.5
37
41.5
4th floor near plant area south side
water noise prevalent
57.4
53.4
49.3
45.2
42
42.4
39.7
31.6
22.6
43
46.6
4th floor as above without water noise
pumps off, therefore no water noise
57.8
52.2
49.2
44.9
38.5
32.8
27.1
21.3
14.3
35
40.8
East Wing chillers in-between chillers, 2 compressors and 2 sets of fans
no specific tonal noise
69.1
67.9
68.3
71.2
70.7
67
59.2 51.2 41.1 68 71.3
underneath chillers on 3rd floor
cannot hear chillers
61.4
54.5
50.1
42.4
36
29.3
24.7
20.7
17.2
33
39
West Wing
street area 3rd floor
59.7
56.2
51.8
49.1
44.6
39.8
34.5
32.2
27
41
46.3
3rd floor central area
water noise present
60.5
57.1
52
45.6
38.8
39.7
37.3
31.2
24.7
40
44.9
3rd floor central area
pumps off, therefore no water noise
60.2
57.2
52.3
45.7
38.7
32.8
25.5
20.2
18.1
36
41.7
3rd floor near door on south side
pumps off, therefore no water noise
60.2
55.5
49.7
43.3
36.7
28.7
23
19.9
15.9
34
39.3
2nd
floor
general
61.4 55.2 51.5 45 37.4 30.9 25.1 21.1 18.7 35 40.7
2nd floor under noisy FCU
sounds like fcu rattling
61.5
57.1
54
49.3
40.7
35.4
24.3
19.2
15.1
40
44.1
ground
floor
near
door
60.8 57.7 53.9 48.6 40.1 34.4 27.1 24.2 18.5 39 43.7
ground floor at edge of street
60.9
57.4
52.3
46.7
39.1
32.5
27.3
25
20.2
37
42.3
West Wing chillers 4th floor near plantroom
chiller noise dominant (tonal 250/500Hz)
65.6
52.5
53.4
57.1
39.9
35
28.4
21.3
17.7
49 49
underneath chillers on 3rd floor
chiller noise dominant (tonal 250/500Hz)
63.6
58.3
54.5
50.3
43
36.6
30.9
28.5
24.2
41
45.8
west wing 4th floor near plantroom
one chiller only running, tone eliminated
66.9
52.9
50.4
47.3
39.3
34.8
29.3
27.8
22.1
38
42.7
around 1m from chillers, both on
subjectively chiller closer to office noisier
73
72.6
71.3
80.6
78.8
76.5
67.9
60.4
52.1
77
80.2
around 1m from chiller, one on only
one chiller only
70.6
69
64.7
69.9
67.9
67.3
55.6
48
44.8
67
70
Measurements as taken on the 12 June 2004
Page:
2
Doc. 29B
C:\Documents and Settings\david.tinsley.DERRY-BS\Local Settings\Temporary Internet Files\OLK679\Chiller Acoustic Resultst_ar180604_memo on chiller repeat measures.doc
Building
Description
Comment
31.5 Hz 63 Hz 125 Hz 250 Hz 500 Hz 1.0 k
2.0 k
4.0 k
8.0 k
NR
Leq
West
Wing
chillers
4th
floor
near
plantroom
no
chiller,
pumps
etc.
only
51.9 53.8 52.5 44.1 36.7 34.1 30.5 25.3 20.6 35.1 41.8
4th floor near plantroom, chillers on tonal noise at 250Hz dominant
53.7
56.2
53.4
54.8
39
36.8
31.9
26.5
21
46
47.5
4th floor near plantroom, chillers on tonal noise at 250Hz dominant
60.3
60.8
58.7
52.8
38.9
37.8
32.1
21.8
15.4
43.9
47.4
in-between chillers, both on
Subjectively much better than on previous inspection
67.3
70.7
70.6
73
74.3
72.1
63.1
52.5
44.2
72.1 75.4
no chiller, pumps etc. only
no chiller, pumps etc. only
54.2
53.7
52.9
45.3
36.3
33.8
29.3
26.1
28.7
35.8
42.2
Chiller turned off,
tonal noise from chiller at 250Hz audible, but not as high as
then back on again 4th floor near plantroom
previously
53.1 51.4 52.6 50.3 36.7 33.3 28.3 18.5 14.1 41.2 43.9
4th floor near plantroom
tonal noise from chiller barely audible
53.5
54.2
53.1
44.5
37.5
35.7
30.9
20.8
15.1
35.7
42.4
Measurements as taken on the 18 June 2004
