Several comments and comprehensive bibliographical references are also provided for each drawn page to enlarge the range of subjects or exercises that can be discussed in courses and foster further readings. Seven drawn pages constitute a visual support to explain the origin and history of the decibel, together with examples from acoustics and other domains on the use of logarithmic scales and classical decibel calculations. This paper is an example of how educational comics can be designed and used to introduce one of the most commonly discussed topics when the basics of acoustics are taught: decibel level. While they are valuable resources for researchers, these books might appear a little daunting for a young audience or for people who are new to acoustics. In fact, the fields of acoustics cover an especially broad range of subjects and domains, and comprehensive acoustics textbooks are usually quite thick as a consequence. Logarithms (or logs for short) are simply a way of describing numbers which vary by very large amounts in a much smaller range.Acoustics is generally defined as the science that deals with the production, transmission, and reception of sound and the understanding and control of its effects. Just about every piece of audio equipment (microphones, loudspeakers, sound cards, amplifiers, mixers, etc) will have specifications expressed as logarithms (i.e. We need to get familiar with the idea of a logarithm. The decibel is a better fit to how our brains perceive sound. The relationship between perceived loudness and the decibel is a straight line. Learn how decibels are used to measure sound intensity and power in a logarithmic scale. On the next graph below, a logarithmic decibel scale is used and now the curve becomes a straight line. Our ’10x’ rule means that as the overall level increases, we need increasingly large changes in intensity to get a similar change in loudness. A-weighted decibels, or dBA, are often used when describing sound level recommendations for healthy listening. Sometimes we use different versions of decibels. An intensity of 1,000 is also half as loud as an intensity of 10,000. Using the logarithmic decibel scale, if a sound is 80 decibels, and we add another 10 decibels, the sound will be ten times more intense, and will seem about twice as loud to our ears. So an intensity of 1,000 is twice as loud as an intensity of 100. To make a sound twice as loud, you need to multiply its intensity by about 10. In the graphs below, the x-axis represents the perceived loudness of a sound, and the y-axis represents the acoustic intensity needed to create that loudness. After analysis, I could offer various recommendations to rectify the issue − all distinctly individual from each other, as acoustics can be affected by nearly everything!” Rob Bungay, Acoustic Consultant, WSP What are decibels? To understand and try to reduce these causes of complaints, among other things I installed sound level meters throughout the room to record noise levels during the day and night, and used acoustic models of the space to assess changes within the room. “I recently worked on a multi-bed intensive care ward where patients and visitors were complaining about the intrusive noise made by the alarms from bedside monitors. In acoustical and audio engineering, decibels are used everywhere because knowing how loud a sound is important whether you’re assessing whether the noise from a new road is going to be a problem or setting the loudness of music in an arena. Graphic: Nick Maroulis Where are decibels used? When a sound is perceived to double in loudness, this corresponds to roughly an increase in 10 dB. It makes things easier if a logarithmic scale is used this is what the decibel scale is. So, to express levels of sound meaningfully in numbers that are more manageable, a logarithmic scale is used, using 10 as the base, rather than a linear one. The ratio of intensities between silence and ‘ow that hurts my ears’ is about 1:100 million million. The human ear is capable of hearing very quiet (low intensity) sounds and extremely loud (high intensity) sounds.
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