noiseStation™ Acoustic Evidence Report

Summary Metrics

LEQ(A) OVERALL

41.9dB

LEQ(A) DAYTIME

—dB

LEQ(A) NIGHTTIME

41.9dB

LDN (DAY-NIGHT AVG)

51.9dB

C−A (LF DOMINANCE)

8.1 dB

L10 AVG

41.9dB

L90 (BACKGROUND)

39.8dB

BEAT DETECTED

98%

EPOCHS RECORDED

82

Regulatory Compliance

STANDARD	LIMIT	METRIC	MEASURED	EXCEEDANCE	STATUS
SM Municipal Code §7.30.040	50.0 dB(A)	Leq(A) Daytime	— dB(A)	—	COMPLIES
SM Municipal Code §7.30.040	45.0 dB(A)	Leq(A) Nighttime	41.9 dB(A)	—	COMPLIES
General Plan N-P1.1	45.0 dB	Ldn	51.9 dB	6.9 dB	EXCEEDS
EPA 1974 Levels (Interior Residential)	45.0 dB	Ldn	51.9 dB	6.9 dB	EXCEEDS
CEQA Significance Threshold	45.0 dB	Ldn	51.9 dB	—	SIGNIFICANT

Tonal and Beat Frequency Analysis (ANSI S12.9 Part 4)

200 HZ HVAC BLADE PASS TONE

196.82 Hz

195.2 MIN Hz

198.4 MAX Hz

3.3 DRIFT Hz

— AVG TNR dB

Thermal drift of 3.3 Hz confirms mechanically-driven source.
TNR > 8 dB satisfies ANSI S12.9 Part 4 tonal criterion.

BEAT FREQUENCY (AMPLITUDE MODULATION)

13.71 Hz

12.6 MIN Hz

17.1 MAX Hz

98% OF EPOCHS

80 EPOCHS

Beat at 13.7 Hz detected in 98% of epochs.
Consistent with two HVAC units operating at slightly different speeds.

Time Series

LEQ(A) — 30s EPOCHS · DAYTIME LIMIT (50 dB) · NIGHTTIME LIMIT (45 dB)

Spectral Analysis

1/3 OCTAVE BAND AVERAGE LEQ (dB)

24-HOUR LEQ(A) RADIAL CLOCK

Measurement Equipment and Methodology

PARAMETER	VALUE
Microphone	Dayton Audio UMM-6 USB Measurement Microphone
Serial Number	2481685
Calibration File	2481685.txt (factory calibration)
Cal Offset	124.16 dB dB
Platform	Raspberry Pi 3 A+ · noiseStation™ Sentinel
Sample Rate	44,100 Hz
Epoch Duration	30 seconds
Frequency Analysis	1/3 Octave Bands, ANSI S1.11-2004 / IEC 61260-1:2014
Tonal Detection	ANSI S12.9 Part 4 — TNR and PR criteria
Weighting	A, C, Z — IEC 61672-1:2013
Location Type	indoor
Measurement Height	1.2 m m