#Sound reference level download

Class 2 SLMs are slightly less accurate, but still suitable for most general sound level measurement purposes. Class 1 SLMs are very precise and suitable for taking lab-quality sound level measurements.

#Sound reference level download

Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.Use a class 1 or class 2 sound level meter (SLM) to get an accurate reading. View our suggested citation for this chapter. Share a link to this book page on your preferred social network or via email. To search the entire text of this book, type in your search term here and press Enter. Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text. Also, you can type in a page number and press Enter to go directly to that page in the book. Jump up to the previous page or down to the next one. or use these buttons to go back to the previous chapter or skip to the next one. Show this book's table of contents, where you can jump to any chapter by name. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.ĭo you want to take a quick tour of the OpenBook's features? No Thanks Take a Tour » You're looking at OpenBook, NAP.edu's online reading room since 1999. APPENDIX C COMPARISON OF YEARLY SOUND ENERGY FROM OCEANOGRAPHIC RESEARCH AND SUPERTANKERS 74–75.APPENDIX B AN INTRODUCTION TO MARINE MAMMALS 65–73.APPENDIX A COMPARISON OF SOUND-PRESSURE REFERENCE LEVELS IN AIR AND WATER 63–64.2 REGULATORY BARRIERS AND POSSIBLE ALTERNATIVES 25–39.Thus, great care must be taken in comparing sound levels in air with sound levels in water. The same source in water radiating the same pressure generates about 4.7 x 10 -13 W/cm 2-an intensity ratio of about 5,000. For example, a spherical sound source radiating a pressure of 1 dyne per square centimeter in air generates about 2.5 x 10 -9 watts per square centimeter. Another is that, because the impedances of air and water differ, the actual power flow in them differs even if the pressures are the same. The difference in reference pressure level is one complication in comparing sound in air with sound in water. Table A-1 gives both levels for some airborne sounds, and also shows the levels of some marine mammal sounds under water. These two references are, therefore, 26 dB apart (20 log 20 = 26). This level is called sound-pressure level (SPL). In air, the common reference is 20 μPa, because that is near the absolute threshold for a normal human listener for a sound frequency of 1,000 Hz. In water, the common reference has been 1 micropascal (1 μPa, or one millionth of a pascal a pascal is 1 newton per square meter). Unfortunately, researchers studying sound in water and air typically use a different reference pressure. The reference level is analogous to sea level in our specification of the height of some land mass. Some small pressure is used as a reference pressure, and any other sound pressure is described as a level above that reference pressure.

Comparison of Sound-Pressure Reference Levels in Air and Waterīecause of its enormous range, sound amplitude is often described in logarithmic units, decibels (dB).