UBLIC HEARING: Director of Development ... - City of Glendale

Arup Acoustics
Ms. Ricarda Bennett
May 15, 1996
Page 2
of two widely used metrics, Equivalent continuous sound level and Community Noise Equivalent
Level as follows:
Equivalent Sound Level- Symbolized by Leq, this measure represents the level of a continuous
steady sound which over a specified time period contains the same total sound energy as the
actual time varying sound of interest,
Community Noise Equivalent Level- Symbolized by CNEL, this rating represents an energy
averaged noise level over a 24-hour period. Noise levels measured during evening hours of 7:00
p.m. to 10:00 p.m. and night time hours of 10:00 p.m. to 7:00 a.m. are adjusted (increased) by 5dB
and 10dB, respectively. These time of day adjustments are included to account for the apparent
increased sensitivity to and annoyance at noise during the evening and night time hours.
EXISTING AMBIENT SOUND ENVIRONMENT
The existing noise levels at the Crystal Springs Site and neighboring residential areas are
influenced primarily by the Ventura and Golden States Freeways, street and railroad traffic. In
particular, the sound environment at the neighboring homes (North and East of the Crystal Spring
Site) is dominated by vehicular traffic noise from San Fernando Way and frequent train operations
along San Fernando Way.
Overall, on an hourly Leq basis the current sound environment ranges between 54 dBA
(recorded at 1:00 a.m.) and 64 dBA (recorded at 6:00 a.m.). On a 24-hour CNEL basis, the current
sound environment was calculated at 67 dBA. The results of the field noise measurements are
shown in Table 1.
Table 1 - Ambient Noise Measurements, Leq (1 hour)
Location Starting Time Leq (dBA) Starting Time Leq (dBA) Starting Leq (dBA)
(Hrs) (Hrs) Time
(Hrs)
On site 1500 62.7 1600 62.9 1700 61.7
1800 62.7 1900 62.3 2000 62.6
2100 62.0 2200 59.5 2300 59.7
2400 56.7 0100 54.3 200 55.0
0300 56.8 0400 60.4 0500 62.2
0600 64.0 0700 63.6 0800 63.6
0900 61.2 1000 61.1 1100 60.1
1200 61.6 1300 61.1 1400 60.3
Neighborhood Duration Leq (dBA)
1 1520-1530 64.0
2 1410-1420 61.0
3 1545-1555 66.0
4 1600-1610 68.0
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