Lecture 1-2: Sound Pressure Level Scale
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NOISE-CON 2004 the Impact of A-Weighting Sound Pressure Level
Baltimore, Maryland NOISE-CON 2004 2004 July 12-14 The Impact of A-weighting Sound Pressure Level Measurements during the Evaluation of Noise Exposure Richard L. St. Pierre, Jr. RSP Acoustics Westminster, CO 80021 Daniel J. Maguire Cooper Standard Automotive Auburn, IN 46701 ABSTRACT Over the past 50 years, the A-weighted sound pressure level (dBA) has become the predominant measurement used in noise analysis. This is in spite of the fact that many studies have shown that the use of the A-weighting curve underestimates the role low frequency noise plays in loudness, annoyance, and speech intelligibility. The intentional de-emphasizing of low frequency noise content by A-weighting in studies can also lead to a misjudgment of the exposure risk of some physical and psychological effects that have been associated with low frequency noise. As a result of this reliance on dBA measurements, there is a lack of importance placed on minimizing low frequency noise. A review of the history of weighting curves as well as research into the problems associated with dBA measurements will be presented. Also, research relating to the effects of low frequency noise, including increased fatigue, reduced memory efficiency and increased risk of high blood pressure and heart ailments, will be analyzed. The result will show a need to develop and utilize other measures of sound that more accurately represent the potential risk to humans. 1. INTRODUCTION Since the 1930’s, there have been large advances in the ability to measure sound and understand its effects on humans. Despite this, a vast majority of acoustical measurements done today still use the methods originally developed 70 years ago. -
6. Units and Levels
NOISE CONTROL Units and Levels 6.1 6. UNITS AND LEVELS 6.1 LEVELS AND DECIBELS Human response to sound is roughly proportional to the logarithm of sound intensity. A logarithmic level (measured in decibels or dB), in Acoustics, Electrical Engineering, wherever, is always: Figure 6.1 Bell’s 1876 é power ù patent drawing of the 10log ê ú telephone 10 ëreference power û (dB) An increase in 1 dB is the minimum increment necessary for a noticeably louder sound. The decibel is 1/10 of a Bel, and was named by Bell Labs engineers in honor of Alexander Graham Bell, who in addition to inventing the telephone in 1876, was a speech therapist and elocution teacher. = W = −12 Sound power level: LW 101og10 Wref 10 watts Wref Sound intensity level: = I = −12 2 LI 10log10 I ref 10 watts / m I ref Sound pressure level (SPL): P 2 P = rms = rms = µ = 2 L p 10log10 2 20log10 Pref 20 Pa .00002 N / m Pref Pref Some important numbers and unit conversions: 1 Pa = SI unit for pressure = 1 N/m2 = 10µBar 1 psi = antiquated unit for the metricly challenged = 6894Pa kg ρc = characteristic impedance of air = 415 = 415 mks rayls (@20°C) s ⋅ m2 c= speed of sound in air = 343 m/sec (@20°C, 1 atm) J. S. Lamancusa Penn State 12/4/2000 NOISE CONTROL Units and Levels 6.2 How do dB’s relate to reality? Table 6.1 Sound pressure levels of various sources Sound Pressure Description of sound source Subjective Level (dB re 20 µPa) description 140 moon launch at 100m, artillery fire at gunner’s intolerable, position hazardous 120 ship’s engine room, rock concert in front and close to speakers 100 textile mill, press room with presses running, very noise punch press and wood planers at operator’s position 80 next to busy highway, shouting noisy 60 department store, restaurant, speech levels 40 quiet residential neighborhood, ambient level quiet 20 recording studio, ambient level very quiet 0 threshold of hearing for normal young people 6.2 COMBINING DECIBEL LEVELS Incoherent Sources Sound at a receiver is often the combination from two or more discrete sources. -
Definition and Measurement of Sound Energy Level of a Transient Sound Source
J. Acoust. Soc. Jpn. (E) 8, 6 (1987) Definition and measurement of sound energy level of a transient sound source Hideki Tachibana,* Hiroo Yano,* and Koichi Yoshihisa** *Institute of Industrial Science , University of Tokyo, 7-22-1, Roppongi, Minato-ku, Tokyo, 106 Japan **Faculty of Science and Technology, Meijo University, 1-501, Shiogamaguti, Tenpaku-ku, Nagoya, 468 Japan (Received 1 May 1987) Concerning stationary sound sources, sound power level which describes the sound power radiated by a sound source is clearly defined. For its measuring methods, the sound pressure methods using free field, hemi-free field and diffuse field have been established, and they have been standardized in the international and national stan- dards. Further, the method of sound power measurement using the sound intensity technique has become popular. On the other hand, concerning transient sound sources such as impulsive and intermittent sound sources, the way of describing and measuring their acoustic outputs has not been established. In this paper, therefore, "sound energy level" which represents the total sound energy radiated by a single event of a transient sound source is first defined as contrasted with the sound power level. Subsequently, its measuring methods by two kinds of sound pressure method and sound intensity method are investigated theoretically and experimentally on referring to the methods of sound power level measurement. PACS number : 43. 50. Cb, 43. 50. Pn, 43. 50. Yw sources, the way of describing and measuring their 1. INTRODUCTION acoustic outputs has not been established. In noise control problems, it is essential to obtain In this paper, "sound energy level" which repre- the information regarding the noise sources. -
Sony F3 Operating Manual
4-276-626-11(1) Solid-State Memory Camcorder PMW-F3K PMW-F3L Operating Instructions Before operating the unit, please read this manual thoroughly and retain it for future reference. © 2011 Sony Corporation WARNING apparatus has been exposed to rain or moisture, does not operate normally, or has To reduce the risk of fire or electric shock, been dropped. do not expose this apparatus to rain or moisture. IMPORTANT To avoid electrical shock, do not open the The nameplate is located on the bottom. cabinet. Refer servicing to qualified personnel only. WARNING Excessive sound pressure from earphones Important Safety Instructions and headphones can cause hearing loss. In order to use this product safely, avoid • Read these instructions. prolonged listening at excessive sound • Keep these instructions. pressure levels. • Heed all warnings. • Follow all instructions. For the customers in the U.S.A. • Do not use this apparatus near water. This equipment has been tested and found to • Clean only with dry cloth. comply with the limits for a Class A digital • Do not block any ventilation openings. device, pursuant to Part 15 of the FCC Rules. Install in accordance with the These limits are designed to provide manufacturer's instructions. reasonable protection against harmful • Do not install near any heat sources such interference when the equipment is operated as radiators, heat registers, stoves, or other in a commercial environment. This apparatus (including amplifiers) that equipment generates, uses, and can radiate produce heat. radio frequency energy and, if not installed • Do not defeat the safety purpose of the and used in accordance with the instruction polarized or grounding-type plug. -
Decibels, Phons, and Sones
Decibels, Phons, and Sones The rate at which sound energy reaches a Table 1: deciBel Ratings of Several Sounds given cross-sectional area is known as the Sound Source Intensity deciBel sound intensity. There is an abnormally Weakest Sound Heard 1 x 10-12 W/m2 0.0 large range of intensities over which Rustling Leaves 1 x 10-11 W/m2 10.0 humans can hear. Given the large range, it Quiet Library 1 x 10-9 W/m2 30.0 is common to express the sound intensity Average Home 1 x 10-7 W/m2 50.0 using a logarithmic scale known as the Normal Conversation 1 x 10-6 W/m2 60.0 decibel scale. By measuring the intensity -4 2 level of a given sound with a meter, the Phone Dial Tone 1 x 10 W/m 80.0 -3 2 deciBel rating can be determined. Truck Traffic 1 x 10 W/m 90.0 Intensity values and decibel ratings for Chainsaw, 1 m away 1 x 10-1 W/m2 110.0 several sound sources listed in Table 1. The decibel scale and the intensity values it is based on is an objective measure of a sound. While intensities and deciBels (dB) are measurable, the loudness of a sound is subjective. Sound loudness varies from person to person. Furthermore, sounds with equal intensities but different frequencies are perceived by the same person to have unequal loudness. For instance, a 60 dB sound with a frequency of 1000 Hz sounds louder than a 60 dB sound with a frequency of 500 Hz. -
Sound Power Measurement What Is Sound, Sound Pressure and Sound Pressure Level?
www.dewesoft.com - Copyright © 2000 - 2021 Dewesoft d.o.o., all rights reserved. Sound power measurement What is Sound, Sound Pressure and Sound Pressure Level? Sound is actually a pressure wave - a vibration that propagates as a mechanical wave of pressure and displacement. Sound propagates through compressible media such as air, water, and solids as longitudinal waves and also as transverse waves in solids. The sound waves are generated by a sound source (vibrating diaphragm or a stereo speaker). The sound source creates vibrations in the surrounding medium. As the source continues to vibrate the medium, the vibrations propagate away from the source at the speed of sound and are forming the sound wave. At a fixed distance from the sound source, the pressure, velocity, and displacement of the medium vary in time. Compression Refraction Direction of travel Wavelength, λ Movement of air molecules Sound pressure Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average, or equilibrium) atmospheric pressure, caused by a sound wave. In air the sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit for sound pressure p is the pascal (symbol: Pa). 1 Sound pressure level Sound pressure level (SPL) or sound level is a logarithmic measure of the effective sound pressure of a sound relative to a reference value. It is measured in decibels (dB) above a standard reference level. The standard reference sound pressure in the air or other gases is 20 µPa, which is usually considered the threshold of human hearing (at 1 kHz). -
Guide for the Use of the International System of Units (SI)
Guide for the Use of the International System of Units (SI) m kg s cd SI mol K A NIST Special Publication 811 2008 Edition Ambler Thompson and Barry N. Taylor NIST Special Publication 811 2008 Edition Guide for the Use of the International System of Units (SI) Ambler Thompson Technology Services and Barry N. Taylor Physics Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899 (Supersedes NIST Special Publication 811, 1995 Edition, April 1995) March 2008 U.S. Department of Commerce Carlos M. Gutierrez, Secretary National Institute of Standards and Technology James M. Turner, Acting Director National Institute of Standards and Technology Special Publication 811, 2008 Edition (Supersedes NIST Special Publication 811, April 1995 Edition) Natl. Inst. Stand. Technol. Spec. Publ. 811, 2008 Ed., 85 pages (March 2008; 2nd printing November 2008) CODEN: NSPUE3 Note on 2nd printing: This 2nd printing dated November 2008 of NIST SP811 corrects a number of minor typographical errors present in the 1st printing dated March 2008. Guide for the Use of the International System of Units (SI) Preface The International System of Units, universally abbreviated SI (from the French Le Système International d’Unités), is the modern metric system of measurement. Long the dominant measurement system used in science, the SI is becoming the dominant measurement system used in international commerce. The Omnibus Trade and Competitiveness Act of August 1988 [Public Law (PL) 100-418] changed the name of the National Bureau of Standards (NBS) to the National Institute of Standards and Technology (NIST) and gave to NIST the added task of helping U.S. -
21-4 Sound and Sound Intensity One Way to Produce a Sound Wave in Air Is to Use a Speaker
Answer to Essential Question 21.3: Doubling the angular frequency, ", causes the frequency to double in part (a). This, in turn, means that that wave speed must double, in part (b). In part (c), the tension is proportional to the square of the speed, so the tension is increased by a factor of 4. In part (e), the maximum transverse speed is proportional to ", so the maximum transverse speed doubles. Finally, in part (f) we get a completely different value, y = – 0.39 cm. 21-4 Sound and Sound Intensity One way to produce a sound wave in air is to use a speaker. The surface of the speaker vibrates back and forth, creating areas of high and low density (corresponding to pressure a little higher than, and a little lower than, standard atmospheric pressure, respectively) in the region of air next to the speaker. These regions of high and low pressure (the sound wave) travel away from the speaker at the speed of sound. The air molecules, on average, just vibrate back and forth as the pressure wave travels through Medium Speed of sound them. In fact, it is through the collisions of air molecules that the sound wave is propagated. Because air molecules are not coupled Air (0°C) 331 m/s together, the sound wave travels through gas at a relatively low Air (20°C) 343 m/s speed (for sound!) of around 340 m/s. As Table 21.1 shows, the Helium 965 m/s speed of sound in air increases with temperature. Water 1400 m/s Steel 5940 m/s For other material, such as liquids or solids, in which there Aluminum 6420 m/s is more coupling between neighboring molecules, vibrations of the Table 21.1: Values of the speed of atoms and molecules (that is, sound waves) generally travel more sound through various media. -
Frequency Response and Bode Plots
1 Frequency Response and Bode Plots 1.1 Preliminaries The steady-state sinusoidal frequency-response of a circuit is described by the phasor transfer function Hj( ) . A Bode plot is a graph of the magnitude (in dB) or phase of the transfer function versus frequency. Of course we can easily program the transfer function into a computer to make such plots, and for very complicated transfer functions this may be our only recourse. But in many cases the key features of the plot can be quickly sketched by hand using some simple rules that identify the impact of the poles and zeroes in shaping the frequency response. The advantage of this approach is the insight it provides on how the circuit elements influence the frequency response. This is especially important in the design of frequency-selective circuits. We will first consider how to generate Bode plots for simple poles, and then discuss how to handle the general second-order response. Before doing this, however, it may be helpful to review some properties of transfer functions, the decibel scale, and properties of the log function. Poles, Zeroes, and Stability The s-domain transfer function is always a rational polynomial function of the form Ns() smm as12 a s m asa Hs() K K mm12 10 (1.1) nn12 n Ds() s bsnn12 b s bsb 10 As we have seen already, the polynomials in the numerator and denominator are factored to find the poles and zeroes; these are the values of s that make the numerator or denominator zero. If we write the zeroes as zz123,, zetc., and similarly write the poles as pp123,, p , then Hs( ) can be written in factored form as ()()()s zsz sz Hs() K 12 m (1.2) ()()()s psp12 sp n 1 © Bob York 2009 2 Frequency Response and Bode Plots The pole and zero locations can be real or complex. -
Computational Entropy and Information Leakage∗
Computational Entropy and Information Leakage∗ Benjamin Fuller Leonid Reyzin Boston University fbfuller,[email protected] February 10, 2011 Abstract We investigate how information leakage reduces computational entropy of a random variable X. Recall that HILL and metric computational entropy are parameterized by quality (how distinguishable is X from a variable Z that has true entropy) and quantity (how much true entropy is there in Z). We prove an intuitively natural result: conditioning on an event of probability p reduces the quality of metric entropy by a factor of p and the quantity of metric entropy by log2 1=p (note that this means that the reduction in quantity and quality is the same, because the quantity of entropy is measured on logarithmic scale). Our result improves previous bounds of Dziembowski and Pietrzak (FOCS 2008), where the loss in the quantity of entropy was related to its original quality. The use of metric entropy simplifies the analogous the result of Reingold et. al. (FOCS 2008) for HILL entropy. Further, we simplify dealing with information leakage by investigating conditional metric entropy. We show that, conditioned on leakage of λ bits, metric entropy gets reduced by a factor 2λ in quality and λ in quantity. ∗Most of the results of this paper have been incorporated into [FOR12a] (conference version in [FOR12b]), where they are applied to the problem of building deterministic encryption. This paper contains a more focused exposition of the results on computational entropy, including some results that do not appear in [FOR12a]: namely, Theorem 3.6, Theorem 3.10, proof of Theorem 3.2, and results in Appendix A. -
A Weakly Informative Default Prior Distribution for Logistic and Other
The Annals of Applied Statistics 2008, Vol. 2, No. 4, 1360–1383 DOI: 10.1214/08-AOAS191 c Institute of Mathematical Statistics, 2008 A WEAKLY INFORMATIVE DEFAULT PRIOR DISTRIBUTION FOR LOGISTIC AND OTHER REGRESSION MODELS By Andrew Gelman, Aleks Jakulin, Maria Grazia Pittau and Yu-Sung Su Columbia University, Columbia University, University of Rome, and City University of New York We propose a new prior distribution for classical (nonhierarchi- cal) logistic regression models, constructed by first scaling all nonbi- nary variables to have mean 0 and standard deviation 0.5, and then placing independent Student-t prior distributions on the coefficients. As a default choice, we recommend the Cauchy distribution with cen- ter 0 and scale 2.5, which in the simplest setting is a longer-tailed version of the distribution attained by assuming one-half additional success and one-half additional failure in a logistic regression. Cross- validation on a corpus of datasets shows the Cauchy class of prior dis- tributions to outperform existing implementations of Gaussian and Laplace priors. We recommend this prior distribution as a default choice for rou- tine applied use. It has the advantage of always giving answers, even when there is complete separation in logistic regression (a common problem, even when the sample size is large and the number of pre- dictors is small), and also automatically applying more shrinkage to higher-order interactions. This can be useful in routine data analy- sis as well as in automated procedures such as chained equations for missing-data imputation. We implement a procedure to fit generalized linear models in R with the Student-t prior distribution by incorporating an approxi- mate EM algorithm into the usual iteratively weighted least squares. -
Sound Intensity and Power
Sound intensity and power Professor Phil Joseph Departamento de Engenharia Mecânica IMPORTANCE OF SOUND INTENSITY AND SOUND POWER MEASUREMENT . Sound pressure is the quantity usually used to quantify sound fields. However, it is often satisfactory as an measure of source because the pressure propagates as a wave which, due to multi-path interference, may lead to fluctuations with observer position. Sound pressure, unlike measures of sound energy, are not conserved. Performance of noise control systems often specified in terms of energy, e.g., transmission loss, absorption coefficient. INSTANTANEOUS INTENSITY Instantaneous sound intensity I(t) is the rate of acoustic energy flowing through unit area in unit time (Wm-2). If, in a point in space, the acoustic pressure p(t) produces at the same point a particle velocity u(t), the rate at which work is done on the fluid per unit area I(t) at time t is given by It ptut Note that I is a vector quantity in the direction of the particle velocity u ‘PROOF’ The work done on the fluid by Force F acting over a distance d in the direction of the force is Fd The work done per unit area A in unit time T, i.e., the sound intensity, is given by F d I x pu A T EXAMPLES FOR WHICH SOUND INTENSITY AND MEAN SQUARE PRESSURE ARE SIMPLY RELATED 1. Plane progressive waves 2. Far field of a source in free field 3. Hemi-diffuse field However, in general there is no simple relation between intensity and pressure ENERGY CONSERVATION Net rate of change of energy = Rate of energy in – Rate of energy out E I I xy x xy y xy t x t In 3 - dimensions E I I I .It 0 .I x y z t x x x RELATIONSHI[P BETWEEN SOUND IINTENSITY AND SOURCE SOUND POWER Applying Gauss's divergence theorem .A dV A.nˆ dS V S to E .I 0 t gives E W dV I.nˆ dS V t S GENERAL PROPERTIES OF SOUND INTENSITY FIELDS Sound intensity (sometimes called sound power flux density) is a vector quantity acting in the direction of the particle velocity vector u(t).