Hi Jeff and Everyone,
I often participate in environmental health practicums that involve matching up local university classes focused on environmental health and local community concerns. These tend to be at the masters level but occasionally have doctoral candidates and undergrads as well. Once in a while high school groups also focus on similar issues, soemtimes during afterschool or summer programs.
A few years back one of these practiums, at BU SPH, used NoiseTube software and found that several different models of Android and iPhones worked well with this software in calibrating overhead jet noise, even in the 45 to 55 DBA range. For example iPhone 4s, which should be especially affordable these days, worked quite admirably.
More recently, STEP in Somerville has acquired a set of REED 4023 noise meters which I have used with Northeastern seniors and which several neighborhoods in Belmont MA are deploying right now in a new 2017 Spring semester university / community practicum, based again at a BU SPH class.
Folks might also want to check out Erica Walker's web-site noiseandthecity - see link below. Erica was a Tufts UEP Master's student when she did a thesis on community noise in Somerville MA, under current UEP Chair Mary Davis, for which I served as reader.
Erica then went right into a Harvard SPH doctoral program which she is just now wrapping up, focused very holistically on community noise in all ranges, with many different sources, including low frequency. Erica has done a huge amount of monitoring in neighborhoods of Boston and adjoining communities, using portable equipment she moves around via bicycle.