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Item 6B Noise AssessmentMike Fann @ Associates Consultants in Noise and Vibration Southlake Commons Noise Assessment Prepared for: Conifer Real Estate 260 Miron Dr., Suite 108 Southlake, TX 76092 Prepared by: Mike Fann Mike Fann & Associates 2132 Brookgate Grapevine, TX 76051 ber 7, 2016 Item 6B - Noise Assessment Southlake Commons Noise Assessment September 7, 2016 Executive Summary The Southlake Commons development initially builds three buildings along FM 1709. This assessment investigates a possible drive through order board noise intrusion into the community. The order board would be placed on the southeast corner of Building 3. Order board sound volumes were measured at a surrogate retail operation. The reference level for that measurement is 80 dBA @ 3' or 62 dBA @ 25'. This is a maximum level, not an average. Any average level is lower. Southlake Commons Site Plan Figure 1 tiLot 7l 91dg:3 1 L 9Plm-Lat916g.3 _ y One urod I 2 f. �m 1 161 dI � 7=0. WntlerrwF) 1 , �'549�l .-----^..•"_'. I flrde%t Boa.4,� m 1 s 11 1595.W 1 'gn8�ry nA 5}ay 1 '1 �; L.uo, C.—W a LUL419169.4 ! I L9k5/$169:5 .1. L9t6 Mo.� 0.ft.'' ! Qx 54cry I. Ona SMr 5,9RIA(neerlw11 5'552f.((( marl I S,M&f.l rdw o_ / O I: F . r • . - 9t39NLTLr ` � � •. Traffic noise is more constant than not. Peak morning rush hour has an average noise at the southern residential property line of 56 dBA and 59 dBA at the offices property line. Site measurements confirm calculations from traffic counts. The lowest measurement during that time period was 52 dBA when the signal light freed White Chapel traffic. The order board volume reduces with increased distance. Standard math calculations produce a volume of 39 dBA at the southern residences and 42 dBA at the commercial district. The lower traffic volume produces 52 dBA. As a result, the noise intrusion signal to noise (S -N) ratio is -13 dBA at both the residences and offices. A 0 dBA S -N would predict no audibility, -13 dBA, even more so. Mike Fann, 2132 Brookgate Grapevine TX 76051 1 Item 613 - Noise Assessment Southlake Commons Noise Assessment September 7, 2016 Noise Intrusion Analysis The relative volume of order board activity and the community background noise determine possible intrusion and audibility. The ambient volume is the community background level without the intruding source. The background on this site is dominated by FM 1709 traffic and DFW over flights. White Chapel traffic is not a significant contributor because traffic volumes and speed are much lower than FM 1709. I measured the sound volume of a Starbucks order board (920 E. NW Hwy, Grapevine) at 80 dBA (max) @ 3'. It was clear, highly intelligibility and easily heard over NW Hwy traffic noise. Standard math formulas calculate a reference of 62 dBA at 25', and 39 dBA at the southern property line. This is a maximum level and not an average level I both calculated and measured the background traffic noise of FM 1709 at the southern property line. Peak morning rush hour traffic produces 56 dBA. On August 30, 1 measured levels varying between 52-56 dBA, depending on the stop light at 9:30 AM. The time was selected to be after morning rush hour traffic and before noon traffic. The order board volume of 39 dBA is 13 dBA less than the background. Tliis overall volume comparison is found in the last column of the chart below. Order Board Vol v Ambient —60 Figure 2 a 50 a� 40 .n CU 30 0 20 a 10 0 31.5 63 .125 250 500 1K 2K 4K dBA Frequency (Octave Band Level, dBA) M 8' wooden fence property line ■ 5tarbucks order board vol at property line Figure 2 also shows relative volumes at each of the octave bands. The horizontal scale is similar to key locations on a piano. Middle C is 250 Hz. One octave to the right is 500 Hz. The octave band comparison is an additional evaluation technique that confirms order board inaudibility. In addition, the existing 8' fence on the property line reduces the noise by another 6-10 dBA in the back yards on the other side. Buildings 4-8 also will provide a similar function, but extend the benefit to the second floor locations because the buildings are much higher than the fence. The existing fence provides an additional 10 dBA, reducing the order board volume to just above the threshold of hearing in a quiet laboratory environment. Mike Fann, 2132 Brookgate Grapevine TX 76051 2 Item 613 - Noise Assessment Southlake Commons Noise Assessment September 7, 2016 Traffic Noise Traffic noise is a function of traffic volume, speed and distance from the median. Figure 3 shows the hourly average noise for the morning rush hour. The lines on the figure illustrate the traffic noise level at distances from the road centerline. The noise decreases with increased distances into the subject property. Figure 3 does not take into account the noise reduction benefit of the future buildings. FM 9 An order board at the southeast corner of Building 3 should never be audible at the southern property line. In fact, it should not be audible at the bank property line 25' to the east. The order board is 62 dBA and the traffic noise is 62-67 dBA, with a 0 to -5 dBA S -N. Mike Fann, 2132 Brookgate Grapevine TX 76059 Item 613 - Noise Assessment 3 Southlake Commons Noise Assessment September 7, 2016 Acoustics Terminology Taken from "Protective Noise Levels - Condensed Version of EPA Levels Document" EPA Report No. 55019-79-100, November 1978 ABOUT SOUND Sound occurs when the air vibrates. The vibration produces alternating bands of relatively dense and sparse particles of air, spreading outward from the source in the same way as ripples do on water after a stone is thrown into it. The result of the movement of the particles is a fluctuation in the normal atmospheric pressure, or sound waves. These waves radiate in all directions from the source and may be reflected and scattered or, like other wave actions, may turn corners. When the source stops vibrating, the sound waves disappear almost instantaneously, and the sound ceases. The ear is extremely sensitive to sound pressure fluctuations, which are converted into auditory sensations. Sound may be described in terms of three variables: 1. Amplitude (perceived as loudness) 2. Frequency (perceived as pitch) 3. Time pattern Amplitude Sound pressure is the amplitude or measure of the difference between atmospheric pressure (with no sound present) and the total pressure (with sound present). Although there are other measures of sound amplitude, sound pressure is the fundamental measure and is the basic ingredient of the various measurement descriptors in the next section, "Measurement of Environmental Noise." The unit of sound pressure is the decibel dB. The decibel scale is a logarithmic scale, not a linear one, such as the scale of length. The logarithmic scale is used because the range of sound intensities is so great, that it is convenient to. compress the scale to encompass all of the sounds that need to be. measured. The human ear has an extremely wide range of response to sound amplitude. Sharply painful sound is 10 million times greater in sound pressure than the least audible sound. In decibels, this 10 million to 1 ratio is simplified logarithmically to 140 dB. Another unusual property of the decibel scale is that the sound pressure levels of two separate sounds are not directly (that is, arithmetically) additive. For example, if a sound of 70 dB is added to another sound of 70 dB, the total is only a 3 -decibel increase (to 73 dB), not a doubling to 140 dB. Furthermore, if two sounds are of different levels, the lower level adds less to the higher as this difference increases. If the difference is as much as 10 dB, the lower level adds almost nothing to the higher level. In other words, adding a 60 decibel sound to a 70 decibel sound only increases the total sound pressure level less than one-half decibel. Frequency The rate at which a sound source makes the air vibrate determines frequency. The unit of time is usually one second and the term "Hertz" (after an early investigator of the physics of sound) is used to. designate the number of cycles per second. The human ear and that of most animals has a wide range of response. Humans can identify sounds with frequencies from about 16 Hz (Hertz) to 20,000 Hz. Because pure tones are relatively rare in real life situations, most sounds consist instead of a complex mixture of many frequencies. Mike Fann, 2132 Brookgate Grapevine TX 76051 Item 613 - Noise Assessment 4 Southlake Commons Noise Assessment September 7, 2016 Time Pattern The temporal nature of sound may be described in terms of its pattern of time and level: continuity, fluctuation, impulsiveness, and intermittency. Continuous sounds are produced for relatively long periods. at a constant level, such as the noise of a waterfall. Intermittent sounds are those, which are produced for short periods, such as the ringing of a telephone or aircraft takeoffs and landings. Impulse noises are sounds, which are produced in an extremely short span of time, such as a pistol shot or a hand clap. Fluctuating sounds vary in level over time, such as the loudness of traffic sounds at a busy intersection. MEASUREMENT OF ENVIRONMENTAL NOISE: SOUND DESCRIPTORS EPA has adopted a system of four "sound descriptors" to summarize how people hear sound and to determine the impact of environmental noise on public health and welfare. These four descriptors are: the A -weighted Sound Level, Equivalent Sound Level, and Day -Night Sound Level. They are related, but each is most useful for a.particular type of measurement. The descriptions and some examples of their uses are described below. A -Weighted Sound Level One's ability to hear a sound depends greatly on the frequency composition of the sound. People hear sounds most readily, when the predominant sound energy occurs at frequencies between 1000 to 6000 Hertz (cycles per second). Sounds at frequencies above 10,000 Hertz (such as high-pitched hissing) are much more difficult to hear, as are sounds at frequencies below about 100 Hz (such as a low rumble). To measure sound on a scale that approximates the way itis heard by people, more weight must be given to the frequencies that people hear more easily. A method for weighting the frequency spectrum to mimic the human ear was sought for years. Many different scales of sound measurement, including A -weighted sound level (and also B, C, D, and E -weighted sound levels) have evolved in this search. A -weighting was recommended by EPA to describe environmental noise because it is convenient to use, accurate for most purposes, and is used extensively throughout the world. The A -weighting of frequency is also used in the three descriptors discussed below. When used by itself, an A -weighted decibel value denotes either a sound level at a given instant, a maximum level, or a steady-state level. The following three descriptors are used to summarize those levels, which vary over time. Mike Fann, 2132 Brookgate Grapevine TX 76051 Item 6B - Noise Assessment Southlake Commons Noise Assessment September 7, 2016 Equivalent Sound Level Another method of quantifying the noise environment is to determine the value of steady-state sound, which has the same A -weighted sound energy as that contained in the time -varying sound. This is the measurement descriptor, termed the Equivalent Sound Level (Leq). The Equivalent Sound Level is a single value of sound level for any desired duration, which includes all of the time -varying sound energy in the measurement period. A Leq of 58 dB reflects the sound energy in all the peaks and valleys of the chart below showing instantaneous changes in level with time. All the energy shown in the chart is equivalent to the energy of a continuous sound of 58 dB. M Typical Neighborhood Noise Levels .Figure Al .30 Time in Mum lei IM The major virtue of the Equivalent Sound Level is that it correlates reasonably well with the effects of noise on people, even for wide variations in environmental sound levels and time patterns. It is used when only the durations and levels of sound are relevant and is easily measurable by available equipment. It also is the basis for the Day -Night Sound Level (Ldn). Day -Night Sound Level The Day -Night Sound Level is the A -weighted equivalent sound level for a 24-hour period with an additional 10 dB weighting imposed on the equivalent sound levels occurring during nighttime hours (10 pm to 7 am). Hence, an environment that has a measured daytime equivalent sound level of 60 dB and a measured nighttime equivalent sound level of 50 dB can be said to have a weighted nighttime sound level of 60 dB (50+10) and an Ldp of 60 dB. Exceedance Levels The exceedance statistics document thresholds that are exceeded a percentage of the time. For example, L(so) is a value that is exceeded 90% of the time. Lso is often used to examine the background or ambient level. This is the lower noise threshold that is exceeded 90% of the time. Other exceedance values range from 1 to 99. L, or L(io) provides a statistical value for the highest maximum values. Mike Fann, 2132 Brookgate Grapevine TX 76051 6 Item 6B - Noise Assessment Southlake Commons Noise Assessment September 7, 2016 Typical Noise Levels Table Al provides some general reference for common noise sources and their levels in dBA. Common Noise Source and Their Sound Levels Table Al Source Sound Level dBA Near large 'et at takeoff 140 Air raid siren 130 Threshold of pain 120 Thunder of sonic boom 110 5 axle truck at roadside 100 Power lawn mower at 5' 90 Vacuum cleaner 80 Freeway traffic at 50' 70 Conversational speech 60 Average residence 50 Bedroom 40 Soft whisper at 15' 30 Rustle of leaves 20 Breathing 10 Threshold of hearing 0 Taken from NBS Handbook 119 Mike Fann, 2132 Brookgate Grapevine TX 76051 Item 6B - Noise Assessment ►I