Hands-on Activity: Measuring Noise Pollution
Educational Standards :
Pre-Req Knowledge (Return to Contents)
Familiarity with LEGO NXT kits and software, and ability to read measurements and plot data using graph paper.
Learning Objectives (Return to Contents)
After this activity, students should be able to:
Materials List (Return to Contents)
For each group:
To share with the entire class:
Materials Note: The total cost of all the parts and software bought separately is about $279, which is almost the same as the full LEGO MINDSTORMS Education NXT Base Set, which costs $295 and contains additional tools that might help for other activities. The full LEGO MINDSTORMS Education NXT Base Set is available at http://www.legoeducation.us/eng/product/lego_mindstorms_education_nxt_base_set/2095.
Introduction/Motivation (Return to Contents)
What is noise pollution and why it is considered a source of pollution? People living in big cities are exposed every day to unwanted and harmful sounds such as loud cars and motorcycles, leaf blowers, barking dogs, noisy neighbors, parties, car alarms, police and firefighter sirens. It is common in many neighborhoods to hear people complaining about loud sounds disturbing their personal activities such as rest, sleep, study, entertainment, relaxation and conversation. A sound becomes unwanted when it either interferes with normal activities or disrupts or diminishes a person's quality of life. For example, in a noisy classroom, students may not be able hear the teacher and may become upset or fall behind in learning as a consequence.
How does noise pollution relate to engineering? Environmental engineers measure noise pollution and report recommendations for noise reduction or elimination. Noise control engineers specialize in designing and testing noise insulation technologies and sound-absorbent materials such as acoustical foam and glass fiber. Engineers in various fields ranging from mechanical, aeronautical, industrial, electrical to civil engineering share a common interest in noise pollution reduction. They design new technologies that produce less noise in order to meet recommended standards. Examples of noise protection products are noise neutralizers such as noise-cancelling headphones and noise insulation windows and doors.
Definition and measurement: Noise pollution refers to any unpleasant, damaging or irritating noise that has the potential to harm people, wildlife or the environment. The decibel (dB) is the main unit used to measure the intensity or loudness of sounds. A sound can also be measured by its pitch, which is the frequency of sound vibrations per second. For example, a low pitch produced by a deep voice, makes fewer vibrations per second than a high voice. Sounds with higher pitch, such as a cry or sound from a violin, have a high rate of vibrations. Sound is usually recorded with a microphone. However, in a sound level meter, a sound sensor is used. Sound sensors work like microphones but are much more accurate.
How does a sound sensor work? The response of a sound sensor to a nearby sound is approximately proportional to the sound pressure, which is the air pressure produced by the propagating sound. For example, if we talk with a piece of paper placed just in front of our mouth, the resulting air pressure causes the paper to move. A similar observation can be made by feeling vibrations from a loud speaker.
What are the sources of noise pollution? Most unwanted sounds are made by transportation vehicles such as airplanes, trains, cars, trucks, buses, motorcycles and construction site equipment such as pneumatic hammers, air compressors, bulldozers, loaders, dump trucks and pavement breakers. Noise can also come from household appliances such as music and television sets, air conditioning, refrigerator, lawn mowers, leaf blowers, loudly talking neighbors or a crowd of people.
Health hazard: According to the World Health Organization (WHO), exposure to levels of noise exceeding safe limits (anything over 50 decibels), can be detrimental to hearing and has the risk of contributing to high blood pressure, strokes and even heart attacks. In fact when the body is exposed to high levels of noise, it reacts by releasing stress hormones and keeping the body in a perpetual level of tension. Long time exposure to loud sounds may result in side-effects such as irritation and anger, lack of concentration, interrupted sleep and hearing-related damage such as tinnitus. The human ear feels pain at 120-140 decibels, and for that reason, we are tend to protect our ears with our hands when listening to sounds in or above that decibel range.
Environmental threat: Plants require cool and peaceful environments to grow, and noise pollution causes poor crop quality. Noise has ripple effects on long-lived plants such as trees and the consequences could last for decades, even after the source of the noise goes away, according to lead author Clinton Francis of the National Science Foundation. Birds and other animals change their behaviors in response to human noise, such as the din of traffic or the hum of machinery. Noise creates sound waves that indirectly weaken the edifice of buildings, bridges and monuments and over time, can put buildings in dangerous condition. (See more information at http://www.nsf.gov/news/news_summ.jsp?cntn_id=123538.)
Engineering controls: Due to the increasing concern about noise pollution, engineering controls are designed to eliminate or reduce the level of noise generated, isolate workstations exposed to excessive noise or insulate noisy work areas. For example, noisy equipment and machinery are replaced with newer models that are quieter or isolated in separate rooms equipped with sound-absorbent materials, dampers, mufflers, silencers or barriers. The same materials are used in construction to keep outside noise from coming into homes and classrooms. Today, most cars are equipped with mufflers, aircraft engines are designed to make less noise, and modern subway systems are less noisy.
Vocabulary/Definitions (Return to Contents)
Procedure (Return to Contents)
Before the Activity
Note: The NXT sound sensor can measure sound pressure level up to 90 dB. The following range value must be obtained while measuring sound pressure: 3.6 to 4.5 dB in a silent room, 4.5 to 9 dB for someone talking approximately 20 feet away, 9 to 27 dB for a normal conversation, and 27 to 90 dB for people shouting or music at a high volume. One might consider a margin error of about 5 dB.
With the Students: Measuring Sound Level
Attachments (Return to Contents)
Troubleshooting Tips (Return to Contents)
Make sure the equipment is set up correctly, the battery levels are good and sensors are connected to the correct brick ports.
Make sure the noiseMeter.rbt program is running.
Always calibrate the sensor before gathering data.
Refer to the NXT website for any other issues: http://mindstorms.lego.com/en-us/whatisnxt/default.aspx
Assessment (Return to Contents)
Pre-Activity Survey: Before providing any information, ask students to complete the Measuring Noise Pollution Pre-Activity Survey to the best of their abilities. Reassure students that this is not for a grade so they feel comfortable writing down their ideas, even if they are unsure. Tell them that even if they do not know all the answers at the start of class, they will know them by the end of the activity.
Informal Discussion: Ask students some questions about the subject matter, covering the questions and correct answers to the pre-activity survey. Refer to the Measuring Noise Pollution Pre-Activity Survey Answer Key. Ask the students:
Activity Embedded Assessment
Analysis: While the experiments are being conducted, have students complete the Measuring Noise Pollution Worksheet and a bar graph of their data. Ask students to comment on the procedure to measure the sound intensity during each experiment. To make sure the graph is completed correctly, ask students what they must display on the horizontal axis and what they must display on the vertical axis. Check that students use an appropriate scale that can fit all the recorded data.
Formal Discussion: Ask students to explain the entire procedure in their own words, as if they were explaining the activity to a family member. In particular, ask them to explain noise pollution, its causes, the unit used to measure sound intensity, and the measurement tools used to measure sound levels. Expect students to be able to cite at least three sources of noise pollution, two health hazards related to noise pollution and two manufactured products to reduce noise pollution. Based on the noise levels they measured in the activity, ask students to list noise pollution sources they believe to be over 85 dB. Also discuss with students the role of each individual component in the experiment (that is, the sensor, the brick, the program and the graph).
References (Return to Contents)
Brüel & Kjær. Environnemental Noise Measurement. Cafe Foundation. Accessed January 3, 2013. (This booklet answers many basic questions about environmental noise criteria and environmental noise measurements.) http://cafefoundation.org/v2/pdf_tech/Noise.Technologies/PAV.Environ.Noise.B&K.pdf
Human Noise Has Ripple Effects on Plants: Clamor affects more than birds and other animals. Published March 20, 2012. National Science Foundation. Press Release 12-052. Accessed January 7, 2013. http://www.nsf.gov/news/news_summ.jsp?cntn_id=123538
Noise Control Act of 1972. U.S. Environmental Protection Agency. Accessed January 3, 2013. http://www.epa.gov/air/noise/noise_control_act_of_1972.pdf
ContributorsViolet Mwaffo, Jerib Carson and Qianqian Lin at the Madiba Prep Middle School
Supporting Program (Return to Contents)Applying Mechatronics to Promote Science (AMPS) GK-12 Program, Polytechnic Institute of New York University
Acknowledgements (Return to Contents)
The development of this activity was supported by the Applying Mechatronics to Promote Science (AMPS) Program funded by National Science Foundation GK-12 grant no. 0741714. However, these contents do not necessarily represent the policies of the NSF and you should not assume endorsement by the federal government.