Hearing Freq Volume Lab

Name: _ Date: _09-25-20 Student Exploration: Hearing: Frequency and Volume Vocabulary: decibel, equal-loudness curve, frequency, hertz, logarithm, pitch, threshold, volume Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. A dog whistle emits a sound that dogs can hear but humans cannot. Why do you think dogs can perceive this sound? _They can hear higher frequencies than humans 2. How do you think your ability to perceive different sounds might change as you age? _Your hearing declines over the years so there will be certain frequencies you wont be able to hear anymore Gizmo Warm-up Have you ever wondered how good your hearing is? The Hearing: Frequency and Volume Gizmo allows you to test how well you hear tones at different frequencies. The frequency of a sound wave is measured in hertz (Hz), where 1 Hz is equal to one wave passing each second. Frequency is related to the pitch of a sound, or whether it sounds high (like a whistle) or low (like a tuba). Before you begin, be sure you are in a very quiet setting. Headphones are recommended for this Gizmo. Set the System volume to 1 and click the test button ( ). Adjust the System volume and your computer so that you hear a moderately loud tone when you click test. 1. Drag the 60-Hz slider and the 4,000-Hz slider to the top and click Play for each sound. Describe what you hear. _60-Hz is a low hum and 4000-Hz is a loud whistle 2. In general, how does the frequency of a sound relate to its pitch? _The frequency of a sound is its pitch, the higher or lower the frequency, the higher or lower the pitch 2019 Activity A: Create an equalloudness curve  Return all sliders to their minimum values.  Turn on Show logarithmic grid and Show decibel values. Introduction: The volume, or intensity, of a tone is measured in a unit called the decibel (dB). Decibels are the base-10 logarithm of the ratio of one volume to another. A 10-dB tone is 10 times more powerful than a 0-dB tone. A 20-dB tone is 10 times more powerful than a 10-dB tone and 100 times more powerful than a 0-dB tone. Question: How well do you hear sounds of different frequencies? 1. Calibrate: Set the 1,000-Hz slider to 10 dB and click PLAY. If you can’t hear anything, raise the System volume or increase your computer’s volume until the tone is barely perceptible. 2. Observe: Move all of the sliders to 50 dB. Click Play full sequence (20 sec). What do you notice about the perceived volumes of the tones? _I couldn’t hear most of them but the few I did where quiet 3. Predict: Do you think humans hear low-frequency, medium-frequency, or high-frequency tones the best? Explain why you think so. _I think humans hear medium-frequency tones the best because we cant hear a lot of low or high frequencies 4. Compare: Play the 1,000-Hz tone and the 125-Hz tone. Both of these tones have the same volume in decibels. Which tone appears to be louder to you? _1000-Hz 5. Measure: Adjust the 125-Hz slider until the 125-Hz tone appears to be just as loud as the 1,000-Hz tone. At what decibel level is this the case? _About 60 decibels 6. Gather data: Repeat this procedure for each of the other tones in the Gizmo. Now when you click Play the full sequence, each tone should sound equally loud. Record the decibel level of each tone below (all frequencies in Hz): 30 60 125 250 500 1,000 2,000 4,000 8,000 16,000 70dB 62dB 60dB 60dB 30dB 20dB 30dB 15dB 10dB 60dB (Activity A continued on next page) “ 2019 Activity A (continued from previous page) 7. Make a graph: Draw dots to mark the position of each slider on the graph below. Connect the dots to create an equal-loudness curve. 8. Analyze: What does this equal-loudness curve show? _What decibel frequencies have to be for me to hear them 9. Think and discuss: How do you think your equal-loudness curve will change as you age? _Some frequencies will have to be at higher decibels for me to hear them 10. Experiment: If possible, have your teacher or another adult produce an equal-loudness curve. How does their curve compare to yours, and how did this compare to your prediction? _This is not possible for me right now 2019 Activity B:  Return all sliders to their minimum values.  Check that the sound levels are still calibrated (see procedure at the start of activity A). Thresholds of perception Introduction: A threshold is a minimum amount of a stimulus, such as sound, that can be perceived. In this activity, you will measure your sound thresholds at different frequencies. Question: What are the faintest sounds that you can perceive? 1. Predict: How do you think the equal-loudness curve you will create in this activity will compare to the equal-loudness curve you made in activity A? _Instead of trying to make the frequencies sound like they’re at the same volume, I’m trying to see how loud they have to be for me to even hear them 2. Measure: Play the 1,000-Hz tone at 20 dB. Then decrease the decibels slightly and play the sound again. Adjust the decibels until you have found the faintest sound that you can hear. What is the lowest volume that you can still hear the 1,000-Hz tone? _0dB 3. 4. Gather data: Repeat this procedure for each of the other tones in the Gizmo. Record the minimum decibel level that you can perceive for each tone below (all frequencies in Hz): 30 60 125 250 500 1,000 2,000 4,000 8,000 16,000 70dB 60dB 0dB 0dB 0dB 0dB 0dB 0dB 0dB 0dB Make a graph: Draw the resulting equal-loudness curve on the graph below. 2019 Acti vity B (continued from previous page) 5. Analyze: How does the shape of this equal-loudness curve compare to the shape of the equal-loudness curve you created in activity A? _This curve has a lot less going on then that of the previous curve, this one just flattens out after the beginning 6. Draw conclusions: Based on your investigations, how does your ability to perceive sound vary with pitch? _I have a much harder time hearing lower pitches than I do higher pitches 11. Apply: Humans can hear frequencies up to approximately 20,000 Hz, while dogs can hear frequencies up to around 60,000 Hz. What sound frequency would you expect to be emitted by a dog whistle, which can be heard by dogs but not by humans? Explain. _Anything above 20,000 so maybe 30,000 or full on 60,000Hz 2019