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Airborne Sound
Published in Dhanesh N. Manik, Vibro-Acoustics, 2017
Figure 3.8 shows how a single frequency sound wave, whose dynamic pressure variation was shown in Figure 3.7, can be produced using a tuning fork. A tuning fork vibrates at a single frequency, which is the natural frequency of its arms, and produces regions of compression and rarefaction in its path. These regions are representative of a dynamic pressure that changes above and below the atmospheric pressure at a frequency. In addition to the time variation of dynamic pressure represented in Figure 3.7, a single frequency sound wave also shows variation as a function of distance. The distance between regions of maximum compression or rarefaction remains fixed for a single frequency sound wave and is known as the wavelength. The wavelength and frequency of a single frequency sound wave are related to the speed of sound, co. The dynamic variation of pressure is sensed by our hearing mechanism that gives the sensation of hearing. In a general situation, sound waves of various frequencies from various sources are produced. But we generally have to pay attention to the most dominant ones. However, the sound pressure level at a location can still be computed by using Equation 3.57 by using the rms value of dynamic pressure.
Physics
Published in Keith L. Richards, Design Engineer's Sourcebook, 2017
The tuning fork is a useful instrument for investigating sound because it vibrates at only one frequency in contrast to most musical instruments that produce several different frequencies simultaneously. A struck tuning fork vibrates at a natural frequency dictated by the fork’s characteristics—the dimensions and the material from which it is made. If the stem of a vibrating tuning fork is set on a table top, the tone becomes louder because the fork forces the table top to vibrate. Because the table top has a larger vibrating area, the sound is more intense. This principle of forced vibrations is applied in most musical instruments by using a part of the instrument, such as the piano sounding board to intensify the sound.
Applications and case studies
Published in Roderic S. Lakes, Viscoelastic Solids, 2017
Tuning forks are used as frequency standards in music, in testing of the ear, and in physics [10.8.3]. To a first approximation the fork can be considered as two cantilever bars joined with an offset at the base. Tuning forks are commonly made of aluminum or aluminum alloy. The low loss tangent of aluminum allows the fork to continue vibrating for a long period after it is struck. Some energy is lost through radiation of sound, in addition to the loss due to viscoelasticity in the material.
Maximum voluntary bite force, occlusal contact points and associated stresses on posterior teeth
Published in Journal of the Royal Society of New Zealand, 2020
Ludwig Jansen van Vuuren, Jonathan M. Broadbent, Warwick J. Duncan, John N. Waddell
For the purpose of this study, it was important to measure bite forces between opposing teeth. We were not attempting to measure forces applied across the whole dental arch, or bite forces in any direction other than a straight down clench. Keeping the average buccal-lingual posterior tooth width of 10 mm in mind, the transducer must be narrow enough to record the bite force between two opposing tooth surfaces. Commonly used strain gauge transducers are typically too wide to be able to measure the loads generated between single opposing teeth (Paphangkorakit and Osborn 1997; Isaza et al. 2009; Lappin and Jones 2014; Shushma and Kantly 2016). These typical wide dimensions ensure that the construction material used, will provide enough rigidity to withstand the range of applied loads it will be subjected to. However, a typical open-ended tuning fork-style transducer with a width of 10 mm, would have to be very thick in order to prevent the ends from touching during flexure or plastic deformation at high loads. Thickness of the transducer has an influence on the recorded forces, as some studies indicated that inter-occlusal distance/jaw separation has an influence on bite force and mastication (Bakke et al. 1989, 1990; Hattori et al. 2009; Cabral 2017). Average recorded bite forces seem to increase with increasing jaw separation, reaching a plateau between 14 and 28 mm (Bakke et al. 1990; Bakke 2006; Hattori et al. 2009). Therefore, the dimensions of the assembled transducer needed to be compact in order to accurately record commonly generated maximum bite forces. For this study, these issues were addressed by developing a novel strain gauge transducer consisting of two heat-treated martensitic stainless steel plates with the terminal ends supported in a bridge configuration. The heat-treated steel ensured a high elastic modulus which made it possible to keep the transducer thin, while being able to withstand large bite forces without plastic deformation and keeping the elastic deformation within the limits of the strain gauges. This permitted the transducer to have central bridging plates with an ideal width-to-thickness ratio, allowing the plates to bend in the middle according to the requirements of the strain gauges whilst keeping the width at 10 mm and the total thickness at 10 mm in the bite recording zone (Figure 1).