Time outdoors may include a variety of noises and noise levels. In addition to natural sounds, which can be beneficial (see the “Health Benefits of Nature and Being Outdoors” section in the Health Guidance chapter), there may also be distracting and potentially stressful noises such as those from freeway and street traffic, construction, lawn care, air traffic, and other local activity. With multiple classes sharing outdoor spaces, there may also be interfering noise between classes. A unique complicating factor during COVID-19 is the challenge of hearing each other speak when children and teachers are physically distanced and/or wearing masks. 

The main goal of the strategies described in this document is to help schools that have challenges related to noise create comfortable outdoor learning spaces that allow students and teachers to hear one another clearly without having to raise their voices.

Consider locating outdoor classrooms in spots that are shielded from street noise by buildings or other existing barriers.

Increase the distance between bothersome sound and receiver by moving outdoor learning spaces away from busy roads and, if possible, at least 45 feet away from other student cohorts. This will decrease background noise level in the “classroom,” which in turn will improve the signal-to-noise ratio so the teacher will not have to speak as loudly. A 45-foot distance is predicted to decrease the voice level of someone speaking in a raised voice level (at a 3-foot distance) by more than 20 decibels.

Reduce unwanted sound between outdoor classrooms by orienting teachers’ backs to one another, as shown in Figure 1. 

If noise levels vary throughout the day, adjust schedules so that outdoor learning does not happen at noisiest times.

Reduce sound at the source, perhaps, by implementing emergency COVID-19 noise ordinances near outdoor learning spaces.

Figure 1 (above): An acoustic barrier configured in a T-shape can mitigate street noise from one side. Click on image to view larger.

Place natural or manufactured shields between sound and receiver. The most effective is a “band shell” or “baseball backstop” configuration, which creates a sound shadow zone that reduces environmental noise intrusion into the area in the “shadow zone,” such as in Figure 2.

This can be accomplished with 

• plantings of tall, dense ornamental grasses, hedges, and shrubs

• straw bales stacked between the teacher’s back and the source of noise, as in Figure 3

• hugelkultur mounds or soil berm providing planting space, sound buffering, and screening unwanted views

• foam/fabric panels enclosing the outdoor learning space and overhead (If fabric is within reach of students and staff, it should be laundered regularly.)

• soft surfacing such as grass, mulch, or outdoor carpets underfoot 

• soft materials such as foam or fabric on adjacent building walls to reduce echoes and reverberation. 
  

Figure 2 (above) and Figure 3 (below): An acoustic barrier configured in an H-shape or X-shape can mitigate street noise from two sides. Click on images to view larger.

Seat students with hearing impairments closest to the teacher.

Check your local health guidelines for the current recommended spacing between people outdoors with or without masks and adjust as allowed. You can find your local health department here. For more on local health rules, see our resource, A Brief Guide to Local Health Rules. 

Add physical devices such as these domes to each seat to help catch the sound. These are only recommended when students are seated in a semicircle, circle, or single row. Check current CDC guidelines to see if domes need to be individualized to each student or cleaned between use. 

Consider localized, narrow-dispersion voice amplification devices and assistive listening technology especially for very noisy sites (near a highway or in an airport flight path). For the voice amplification devices, one that seems in alignment with the intent is the BeltBlaster Pro by AVAmplivox. The narrow dispersion loudspeakers would be line array loudspeakers, which are available from many vendors (e.g., Bose, JBL, and others). There would need to be some technical due diligence with respect to speaker layouts and orientation. The BeltBlaster device also has a volume control that would require adjusting by the users.

dB NOISE SOURCE

90 Lawn mower within 20 feet

80 Average city noise near major roadway

70 Freeway traffic about 500 feet away

60 Conversational speech at a distance of 3 feet

If the perimeter of the schoolyard is exposed to regular roadway noises, mitigation may be needed, such as with soft vegetation along a fence.