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© Rational Acoustics LLC 2020 - All rights reserved
Session 6:
“All About SPL”
Operator Fundamentals Online
Smaart Operator Fundamentals OnlineSession 6
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Jamie Anderson◦ President, Director of Training◦ [email protected]
Chris Tsanjoures◦ Smaart Product Manager, Instructor◦ [email protected]
Michael Lawrence◦ Application Support Specialist, Instructor ◦ [email protected]
Gavin Caanan◦ Training Coordinator◦ [email protected]
© Rational Acoustics LLC 2020 - All rights reserved
Smaart Operator Fundamentals OnlineSession 6
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© Rational Acoustics LLC 2020 - All rights reserved
Rational Acoustics LLC32 Crabtree Ln
Woodstock, CT 06281USA
+1 (860) 928-7828
www.RationalAcoustics.com
Smaart Operator Fundamentals OnlineSession 6
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What is SPL?
Why do we measure it?
How do we measure it?
SPL Features in Smaart v8 & Smaart SPL
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Smaart Operator Fundamentals OnlineSession 6
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Sound Pressure Level
An objective measure of the strength of air pressure deviations caused by a sound wave
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A
T
Smaart Operator Fundamentals OnlineSession 6
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Expressed in decibels
Logarithmic scale corresponds well with human hearing (% change)◦ 1 to 2 is perceived as the same increase as 100 to 200
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0 dB SPL – threshold of hearing20 µPa (0.00002 Pa)
120 dB SPL – threshold of pain
1,000,000 : 1
20log(1,000,000/1)= 120 dB
H
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SPL is an objective measurement of physical reality
Human loudness perception is extremely complex, with many factors
◦ Tonal content / balance
◦ Intelligibility
◦ THD
◦ Continuous vs Impulsive
◦ Listener Fatigue
◦ Familiarity and Preference
◦ Context & Program Material
Humans are not particularly reliable judges of SPL
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Smaart Operator Fundamentals OnlineSession 6
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Originally an attempt to produce a measurement that “looks like it sounds”
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What is the goal?
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Sound Engineer awareness of:
◦ Consistency / Quality control
◦ Dynamic Range
◦ Fatigue
◦ Awareness of level somewhere else
Venue awareness:
◦ General / policy / courtesy
◦ Consistency
◦ Nuisance Monitoring
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Smaart Operator Fundamentals OnlineSession 6
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Noise Pollution / Nuisance Noise◦ Not bothering the neighbors
US: No enforced federal law◦ 42 U.S.C. §4901 et seq. (Noise Control Act of 1972)
◦ Largely focused on interstate commerce (appliances, trucks, railroads, etc)
◦ Defunded in 1981, responsibilty shifted to state / local
Many state /local regulations reference ANSI S1.4-1971◦ A-weighted measurement
◦ Ignores the LF energy that is usually the most problematic
◦ Many have poor wording: “Shall not make excessive noise” (???)
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Smaart Operator Fundamentals OnlineSession 6
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Courtesy of Chris Leonard
Inside Venue
Outside Venue
Vs.
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How loud is “too loud?”
When dealing with exposure, the question is twofold:
◦ - How loud?
◦ - How long?
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Smaart Operator Fundamentals OnlineSession 6
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OSHA PELs will not protect you from NIHL (Noise-Induced Hearing Loss)!
NIOSH: Criteria for a Recommended Standard: Occupational Noise Exposure (1998)
https://www.cdc.gov/niosh/docs/98-126/pdfs/98-126.pdf?id=10.26616/NIOSHPUB98126
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OSHA Permissible Exposure Limits
Sound level
(dBA)
Duration
(Hours:Minutes)
85 16:00
90 8:00
95 4:00
100 2:00
105 1:00
110 0:30
115 0:15
120 0:07
NIOSH Recommended Exposure Limits
Sound level
(dBA)
Duration
(Hours:Minutes)
82 16:00
85 8:00
88 4:00
91 2:00
94 1:00
97 0:30
100 0:15
103 0:07
Smaart Operator Fundamentals OnlineSession 6
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dblimits.com
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SPL Slow
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SPL Slow Leq 10
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Leq = Equivalent Continuous Sound Pressure Level
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Important for live events due to fluctuating levels
Allows a statement about level compliance
Leq 10 = 10 minute average
LAeq 10 = A-weighted
https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019N3eSAE&l=en-US
Smaart Operator Fundamentals OnlineSession 6
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Choosing Hardware◦ Calibrator
◦ Mic
◦ Interface
◦ Max SPL = 140 dB SPL
◦ Why 140 dB SPL?
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Smaart Operator Fundamentals OnlineSession 6
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A Slow
C Slow
Peak C
Smaart Operator Fundamentals OnlineSession 6
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140 dB SPL w/o clipping (THD <3%)
Check sensitivity for voltage output at 140 dB SPL◦ iSEMcon EMX-7150: 6 mV/Pa
@ 140 dB SPL: 1.2Vrms (+4 dBu)
◦ EW M30: 34 mV/Pa
@ 140 dB SPL: 6.8Vrms (+19 dBu)
◦ Shortcut: 140 – 94 dB = 46 dB (200x)
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1 Pa = 94 dB SPL
Choose Mic & IO together:
https://www.youtube.com/watch?v=Xcnp5VwV9Hc
(video courtesy of iSEMcon gmbh)
Smaart Operator Fundamentals OnlineSession 6
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Measurement goals dictate accuracy requirement
Consistency: accurate calibration is not important. Hit the same numbers every night.
Noise pollution: numbers need to be meaningful
Exposure: accurate calibration is extremely important.◦ Since exposure times are based on level, an error in measured level correlates directly
to an error in exposure dose
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Smaart Operator Fundamentals OnlineSession 6
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14min
28min
42min
57min
73min
90min
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Class 1 vs Class 2
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Type 1 vs Type 2
Standards?
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IEC 61672-1:2013:◦ Class 1 SPL systems are required to measure over a wider frequency range than a
Class 2 system as well as meet tighter tolerances for performance criteria and documentation. The nitty-gritty details are laid out in the standards document IEC 61672
◦ The differences between Classes are not limited to microphone and interface tolerances (the entire signal acquisition chain is subject to specified tolerances), but also the format and detail with which the measurement data is logged and kept for presentation in a legal setting. It is for this reason that the UI (user interface) displaying the measurement results are also factored in Class compliance.
◦ The stipulations for documentation of SPL information outlined in the IEC standards state that specific data must be reported and documented over the duration of exposure.
Smaart Operator Fundamentals OnlineSession 6
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Smaart Operator Fundamentals OnlineSession 6
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Smaart Operator Fundamentals OnlineSession 6
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National Institute of Standards and Technology (NIST)
Certificate of Traceability
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Smaart Operator Fundamentals OnlineSession 6
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Smaart Operator Fundamentals OnlineSession 6
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Smaart Operator Fundamentals OnlineSession 6
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CDC/NIOSH Study: 130 iOS apps, 3 were within 2 dB
https://blogs.cdc.gov/niosh-science-blog/2014/04/09/sound-apps/
“An analysis of 50 different apps indicated that only one was accurate to within 5 dB.”
https://www.who.int/pbd/deafness/Hearing_loss_due_to_recreational_exposure_to_loud_sounds.pdf
Clipping / overload at concert-level SPLs
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Smaart Operator Fundamentals OnlineSession 6
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10 EaZy WebsiteU.S. www.10eazy.usEverywhere Else: www.10eazy.com
Smaart Operator Fundamentals OnlineSession 6
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Smaart SPL Guide◦ www.rationalacoustics.com/download/SmaartSPLQuickStartGuide.pdf
Smaart SPL Quickstart (Video) ◦ www.youtube.com/watch?v=CvlpGWwwMf0&feature=emb_logo
Calibrating for SPL with Smaart (Video)◦ www.rationalacoustics.com/support/464494-How-do-I-calibrate-Smaart-for-SPL
Smaart SPL Product Page (More Info/More Videos)◦ www.rationalacoustics.com/smaart/smaart-spl/
www.rationalacoustics.com
© Rational Acoustics LLC 2020 - All rights reserved