This activity focuses on the following Three Dimensional Learning aspects of NGSS:ĭevelop a model using an analogy, example, or abstract representation to describe a scientific principle.Īlignment agreement: Thanks for your feedback! Science findings are based on recognizing patterns.Īlignment agreement: Thanks for your feedback! Explain how engineers design technologies to help with hearing loss or injury.ĭevelop a model of waves to describe patterns in terms of amplitude and wavelength and that waves can cause objects to move.Ĭlick to view other curriculum aligned to this Performance Expectation.Describe the amplitude of sound as measured in decibels.Explain that loud sounds can damage hearing. A great understanding of the ear and its physiology is necessary to design these devices.Īfter this activity, students should be able to: A person with a cochlear implant cannot actually hear as a normal person does, but it allows them to have a relationship with speech and hear the environment around them. Together, they collect and send impulses to the brain. The device contains a microphone, a speech processor, a transmitter and electrodes. Cochlear implants are an electronic device that gives a deaf person a sense of sound by surgically implanting the devices under the skin behind the ear. Bioengineers have invented devices to treat deafness, including hearing aids, cochlear implants, placing tubes in the eardrum, and replacing part of the bones in the middle ear with wires. Understanding the level of decibels is necessary for engineers to successfully design devices to fix hearing damage and make new equipment. This engineering curriculum aligns to Next Generation Science Standards ( NGSS). If available, students use a decibel meter to measure sounds. Sound types and decibel readings are written on sheets of paper and students arrange the sounds from the lowest to highest decibel levels. If we were to calculate this using equation (5.3) we would get 87.6 dB SPL - try this for yourself.Students learn the decibel reading of various noises and why high-level readings damage hearing. 85 dB SPL and then add this to the 84 dB SPL which would give us a total of approximately 87.5 dB SPL. We can add the 80.8 and 83 first to give approx. For example if we have 3 measurements of 80.8, 83 and 84 dB SPL. If we have more than two sound levels to add we can simply break them down into a series of pairs. At the right hand of the scales, if the two sound levels differ by as much as 20dB then the lower sound level makes very little difference to the total sound level. 80+1 = 81 dB SPL).Īt the left hand side of the nomogram, if the two sound levels are equal (difference = zero) then we should add 3 dB (i.e. 1 dB) this is then added to the higher sound level (i.e. So for our previous example, we take the difference between the two sound levels (80 - 74 = 6 dB) and read the lower scale to find the correction (approx. It is equivalent to a 3 dB increase in the total sound pressure level.įigure 5.2: Nomogram for addition of decibels If we add two unrelated sounds of the same intensity together, Now since we are talking about plane waves, our total sould pressure level = 83.01 dB SPL. So we now have the sound intensity of our combined signal and we can now convert this back to a dB value: If we now add I 1 and I 2 to give I total we have: If we refer to the two sound intensities as I 1 and I 2 which are both equal, then as we have already seen: I 1 = I 2 = 10 -4 W/m 2 assumptions of a plane wave) then the first thing we need to do is convert our dB SPLs into intensities as in 5.1. If we assume that the value in dB SPL is the same as it would be if we measured it in dB IL (i.e. So, for example suppose we have two independent sound sources producing white-noise and the sound pressure level of each one measured on it's own is 80 dB SPL - our question is, what is the resulting sound pressure level when they are both turned on together?
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