Jeanine Botta – jeanine.botta@downstate.edu
The Right to Quiet Society for Soundscape Awareness and Protection
720 East 31st Street
Apartment 7G
Brooklyn, NY 11210

Popular version of paper 1pNS1
Presented Monday afternoon, May 13, 2019
177th ASA Meeting, Louisville, KY

Based on quieter engines that have evolved over decades with electric, hybrid, and many internal combustion engine vehicles, authoritative voices tell us that the problem of noisy cars has been solved. Moving vehicles may be quieter now, but this is not the case for cars that are stationary.

Most vehicles manufactured for the North American market feature an audible signal that assures owners that they have locked their cars. Roughly half of cars sold in the U.S. and Canada use an electronic tone, while the rest use a horn sound. Most cars offer the option to use a visual signal.

Owners can lock a car and arm its security system without use of any signal, but this feature is rarely discussed when buying a car. With some cars, remote start, stages of battery charging, and stages of filling a tire with air use a horn signal. Some brands have incorporated horn sounds to signify that the engine is running when its driver has left the car.

Many people are unaware of acoustic vehicle signals, or the fact that some horn sounds are emitted from parked cars. Awareness may occur after buying a car or when walking in front of a car that is being locked. When one’s home faces a parking lot or street parking, sleep disruption can occur, and annoyance can affect the ability to return to sleep.

This study was conducted to explore common experiences related to sleep disruption caused by remote horn signaling, using content analysis of online complaints posted in discussion forums and forums created by car owners who want to disable the sound. The study uses a database that was compiled as part of a noise activism endeavor called the Silence the Horns project.

In complaint forum posts, remote horn signals are described as a source of sleep disruption, reduced quality of life, annoyance, and emotional and physical stress responses. Other concerns include hearing health, safety, and legal considerations. Posts can provide useful information, even as some authors introduce a degree of antagonism. [1]

Car owner forum posts are practical. Authors may not mention a reason for wanting to eliminate the horn sound, but when they do, concerns include general consideration for neighbors, specific concerns about sleep disruption of a family member or neighbor, and embarrassment about creating a sound that brings attention. Authors are helpful, often post in other auto topic forums, and set a friendly tone. [2]

Online forum data will continue to be added to the database throughout 2019. It is hoped that auto industry stakeholders might consider sleep disruption to be an important unintended consequence of horn use with lock confirmation in future car models.

If passed, proposed Senate bill S.543, the Protecting Americans from the Risks of Keyless Ignition Technology Act, would protect consumers from the risk of carbon monoxide poisoning related to cars inadvertently left with the engine running. [3, 4] Stakeholders should be aware that consumers are eliminating horn sounds that automakers implemented to discourage leaving a car with the engine running.

References

[1] ParaPundit forum, Locking A Car With A Short Horn Blast Is Rude and Obnoxious
http://www.parapundit.com/archives/002265.html

[2] GM-VOLT: Chevy Volt Electric Car Site, Suppress option for Charging Honk
https://gm-volt.com/forum/showthread.php?37986-Suppress-option-for-Charging-Honk

[3] Blumenthal announces legislation to protect against CO and rollaway risk raised by keyless cars
http://www.norwalkplus.com/nwk/information/nwsnwk/publish/News_1/Blumenthal-announces-legislation-to-protect-against-CO-and-rollaway-risk-raised-by-keyless-cars_np_25124.shtml

[4] S.543 – PARK IT Act
https://www.congress.gov/bill/116th-congress/senate-bill/543

Kent Gee – kentgee@byu.edu
Brent Reichman – brent.reichman@gmail.com
Brigham Young University
N283 Eyring Science Center
Provo, UT 84602

Alan Wall – alan.wall.4@us.af.mil
Air Force Research Laboratory
2610 Seventh Street, Bldg 441
Wright-Patterson Air Force Base, OH 45433

Popular version of paper 1aNS6 Meteorological effects on long-range nonlinear propagation of jet noise from a static, high-performance military aircraft
Presented Monday morning, Nov. 5, 2018
176^th ASA Meeting, Victoria, British Columbia
Read the article in Proceedings of Meetings on Acoustics

The sound of a fighter jet aircraft as it takes off or flies by at high power is unique, in part, because of “crackle.” Crackle, described as sounding like tearing paper or static from a poorly connected loudspeaker, is considered an annoying and dominant part of the overall aircraft noise.  Crackle can be heard several times in this YouTube video of an F-35 at the Paris Air Show.

What causes crackle? This distinct sound quality is caused by shock waves being embedded in the noise radiated from the high-thrust exhaust, which leaves the jet engine traveling much faster than the speed of sound.  These supersonic jet plumes create intense noise levels, such that the noise travels nonlinearly and the speed of sound is no longer independent of sound amplitude.  Faster-traveling, high-pressure parts of the compressive sound wave overtake slower-traveling, low-pressure parts of the wave, creating shock waves that form more readily with increasing sound level. The below animation shows the formation of discontinuous shock waves as part of nonlinear propagation, and the accompanying sound files reveal how nonlinear propagation and shock formation turn a smooth-sounding noise signal into one that contains significant crackle.

This paper describes how shock waves in jet aircraft noise can be affected by local weather changes.  As the shocks travel through the atmosphere, they slowly dissipate.  But, the wind and temperature profiles near the ground can greatly change shock characteristics and, therefore, the crackle heard from a military jet aircraft.  Recent noise measurements of tied-down F-35 aircraft help to describe these changes.  The noise recordings were made at microphones at several distances and angles, but as far as 4000 ft away from the aircraft.  While measurements made short distances from the aircraft show only small differences in shock characteristics with changing temperature and wind, data collected at greater distances than 1000 ft reveal much greater sensitivity to local meteorology.  At 2000 and 4000 ft, cranes were used to elevate microphones as high as 100 ft in the air, and the recordings showed something surprising.  Not only did the sound levels and shock characteristics vary greatly with height, but in some cases the shock content increased with decreasing sound level. This finding conflicts with the usual behavior of nonlinear sound waves.

These results show that nonlinear propagation of jet noise through real atmospheric conditions is more complex than previously anticipated.  More broadly, this study also points to the need to investigate in greater detail how the shock waves and crackle present in jet noise can be impacted by small weather changes. Improved predictions of received noise, including crackle, will help military bases plan aircraft operations to minimize community impact.

Acknowledgment: These measurements were funded by the F-35 Joint Program Office. Distribution A: Approved for public release; distribution unlimited. Cleared 11/2/2018; JSF18-1022. 

Pasquale Bottalico – pb81@illinois.edu

University of Illinois – Department of Speech and Hearing Science
901 South 6th Street
Champaign, IL 61820

Popular version of paper 4aNS11, “Lombard Effect In Restaurant Setting: How Much Would You Spend To Eat At This Restaurant?”
Presented Thursday morning, November 8, 2018, 11:40-12:00 AM, SALON C (VCC)
Joint Meeting 176th ASA Meeting and 2018 Acoustics Week in Canada (CAA), Victoria BC, Canada

This study was conducted to determine the exact point when the noise in a restaurant setting causes vocal discomfort for customers. Another aim of the study was to identify customers’ willingness to spend time and money in a restaurant depending on the varying noise level in the environment.

According to the 2016 Zagat State of American Dining report, 25 percent of restaurant customers consider noise the most irritating component of dining out (Figure 1).

Figure 1. Results from the 2016 National Dining Trends survey of Zagat

The Lombard effect is when speakers unconsciously increase the loudness level of their speech in the presence of background noise in order to be understood. This requires increased vocal effort and can cause vocal fatigue over time. In a restaurant setting particularly, background noise created by other patrons’ conversations is more likely to trigger the Lombard effect than other types of background noise [1] (Figure 2). Previous studies have demonstrated that uncomfortably loud levels of background noise can result in decreased customer satisfaction and business for the restaurant [2, 3].

Figure 2. Example of a noisy restaurant

The Lombard effect has been investigated in a variety of environmental settings with different types and levels of background noise.  However, little is known about the level of background noise that will cause the Lombard effects in restaurant settings.

Fourteen male and 14 female college students with normal hearing were recruited to participate in the study. They read passages to a listener in the presence of typical restaurant noise (as in the attached audio clip) with the level varying between 35 dBA and 85 dBA. Participants were instructed to be sure that the listener could understand them equally well in each condition. (Figure 3)

Figure 3. Experimental setup

Restaurant noise

For each noise condition, the participants were then instructed to answer questions about the disturbance they perceived from the noise, how long they would enjoy spending time in this restaurant setting, and how much money they would spend at this restaurant.

The results showed that both participant vocal effort and disturbance increased as the background noise level increased. Reported willingness to spend time and money at a restaurant decreased as the background noise level increased. The participants started to be disturbed at noise levels higher than 52.2 dB(A) (Figure 4, blue line). Because of the disturbance in the communication, participant vocal effort increased at a doubled rate as the background noise level increased (Figure 4, red line) for noise levels higher 57.3 dB(A) (approximately the level of normal conversational speech). Similar noise levels to the one that starts the communication disturbance (51.3 dB(A) and 52.5 dB(A)) also trigger a decrease in the willingness to spend time and money in a restaurant (Figure 4, green and yellow lines). In conclusion, to improve the acoustic environment of restaurants, background noise levels should be lower than 50-55 dB(A). This will minimize the vocal effort of patrons and the disturbance in their communication. Concurrently, this will increase business for the restaurant since patrons would be willing to spend more time and money to eat in a restaurant with a background noise lower than 50-55 dB(A).

Figure 4. Relationship between the level of the noise in dB(A) and self-reported communication disturbance (blue line), relative voice level (red line), willingness to spend time (green line) and willingness to spend money (yellow line), where the error bands indicate the standard error. Vertical dashed lines mark the change-points.

Bibliography
[1]A. Astolfi and M. Filippi, “Good acoustical quality in restaurants: a comparison between speech intelligibility and privacy,” in Proceedings of EuroNoise (2003).

[2] C. C. Novak, J. La Lopa, and R. E. Novak, “Effects of sound pressure levels and sensitivity to noise on mood and behavioral intent in a controlled fine dining restaurant environment,” Journal of Culinary Science & Technology 8(4), 191-218 (2010).

[3] W. O. Olsen, “Average speech levels and spectra in various speaking/listening conditions: A summary of the Pearson, Bennett, & Fidell (1977) report,” American Journal of Audiology 7(2), 21-25 (1998).