15Measuring, mapping and finding quiet

The short version: A good iPhone app can get within a couple of decibels of a professional meter, which is enough to learn what is loud around you but not, by itself, enough for a formal case. Noise maps from the EU and the US Bureau of Transportation Statistics are computer models of long-term averages, useful for comparing streets and neighborhoods, not readings at your door. Complaints tend to work best when they follow the ladder that official guidance in several countries recommends: talk first, keep a dated log, use the right channel, and try mediation for neighbor disputes. Finding quiet mostly comes down to distance, something solid in the way, and heavy walls - with bass the hardest to stop.

Can I measure noise with my phone?

What you hear: a sound you suspect is "too loud," and a phone in your pocket.

In 2014 the US National Institute for Occupational Safety and Health (NIOSH) looked at 130 iPhone sound meter apps and tested 10, and looked at 62 Android apps, of which 4 "partially met" its criteria. Three apps came within +/-2 dB of a reference meter on A-weighted readings.¹⁶ The best A-weighted results were SoundMeter (a mean difference of -0.51 dBA), NoiSee (-1.12) and Noise Hunter (-1.92). The researchers found the same Android app showed "wide variance" across devices, and concluded Android and Windows developers did not offer apps that met the needs of occupational noise assessment.¹⁴ In a 2015 follow-up, the same researchers reported preliminary results that, with a calibrated external microphone, apps agreed within +/-1 dB of professional instruments.¹⁷

NIOSH then built its own free NIOSH Sound Level Meter app, announced in January 2017. It runs on iOS only and reports LAeq, Lmax, Lpeak, time-weighted average, dose and projected 8-hour dose, with A, C or Z weighting and slow or fast response. In a lab test it read about 2 dBA off with the iPhone's built-in microphone and within 1 dBA with a calibrated external microphone.¹⁰

For context, a 3 dB change is barely perceptible and 5 dB is readily perceptible,⁹ so a 2 dB app error is smaller than most differences you would notice by ear.

What is a real sound level meter?

Professional meters are graded under IEC 61672-1 as Class 1 (precision) or Class 2 (general purpose). At 1 kHz, the allowed tolerance is +/-1.1 dB for Class 1 and +/-1.4 dB for Class 2; at 20 Hz it widens to +/-2.5 dB and +/-3.5 dB.¹⁵ US practice often uses the older ANSI terms Type 1 and Type 2; OSHA treats a Type 2 meter as accurate to +/-2 dBA.¹⁴ Requirements depend on the job: UK workplace rules require at least Class 2, while unattended aircraft monitoring under ISO 20906 requires Class 1.¹⁵

Some UK councils accept recordings from a phone app, though not as decibel readings. Woking Borough Council says it stores recordings sent through The Noise App and "may use them to investigate noise complaints."²⁷⁴ Wrexham accepts Noise App recordings once a complaint has been formally registered, up to ten per complaint; its guidance does not mention decibel readings.²⁷⁵

How do I take a reading that means something?

Match your settings to the rule you care about (local limits are in Who makes the noise rules; the terms are explained in Sound and decibels), and write down how you measured.

• Weighting. Use dBA for most city limits. Use dBC if the problem is bass and your code has a dBC limit, as New York City and Toronto do.^{64 67}
• Metric. Leq is the steady level with the same energy as the fluctuating sound over the period;⁴ Toronto's amplified-sound limits are 10-minute Leqs.⁶⁷ Lmax is the loudest moment and ignores how long it lasted.⁴
• Background. Several codes judge a noise against the ambient level, such as New York City's 7 dB(A) over ambient at night.⁶⁴ L90, the level exceeded 90% of the time, is a common measure of background.⁷ Take a reading with the source off, if you can.
• Response. Fast time weighting averages over 125 milliseconds, slow over 1 second.⁷ Note which one you used.
• Place and distance. Codes measure at specific points, such as a lot line in Boston⁶² or inside a home 3 feet from an open window for New York City air conditioners.⁶⁴ From a single source, the level drops about 6 dB each time the distance doubles,⁵ so a reading without a distance is hard to use.

How do I read a noise map?

What you see: a city map washed in color bands, red along highways and runways fading to green.

A noise map is a model, not a recording. It calculates long-term average levels from traffic counts, flight paths and terrain.

The EU's first round covered cities over 250,000 people, roads over 6 million vehicles a year, railways over 60,000 trains a year and airports over 50,000 movements; the second round, due June 30, 2012, lowered the thresholds to cities over 100,000, roads over 3 million vehicles and railways over 30,000 trains.¹² Lden is a 24-hour average that adds 5 dB to evening noise (7 p.m. to 11 p.m. by default) and 10 dB to night noise (11 p.m. to 7 a.m.); countries may shift the hours.¹¹ Lnight is the night average alone. The Directive "does not set any limit value."²⁵

The BTS map models worst-case conditions with no shielding from buildings or terrain. It found more than 97% of the US population potentially exposed to transportation noise below 50 dBA (24-hour LAeq).²³ Airport maps in the US use contours, lines joining points of equal level, like the lines on a topographic map.⁴

Three cautions. An Lden value and a 24-hour LAeq value are not the same number, because Lden carries evening and night penalties. A model shows an annual average, not the garbage truck at 5 a.m. And worst-case modeling with no shielding can show a building in a quiet courtyard as loud as one facing the road.

How do I complain about noise effectively?

Official guidance from several countries follows a similar ladder.

1. Talk to the source first. An Australian council's advice is to approach the neighbor tactfully before contacting the council.⁶⁸
2. Keep a log. For barking dogs, that council says you may be asked to keep a diary.⁶⁸ Note dates, times, how long the noise lasted, what it was and how it affected you, plus any readings and how you took them.
3. Check whether it is permitted. In Boston, the city advises checking the after-hours construction permit database before reporting night work.¹¹⁵
4. Use the right channel. In New York City, all noise complaints go to 311.⁶³ Many places split the job: in New South Wales, late-night parties go to police, pubs and clubs to Liquor and Gaming NSW, and aircraft to Airservices Australia.⁶⁸ For aircraft, identifying the flight first makes a complaint easier to act on; The Airwaves covers flight trackers.
5. Separate the noise from the relationship. A New York dispute resolution group suggests filing with 311 for the noise and contacting a mediation service, such as the New York Peace Institute, for the relationship with the neighbor.²⁷⁶

Volume is not the same as action. New York City's 311 took more than 738,000 noise complaints in 2024.¹

The most complete public figures are old. A January 2018 New York State Comptroller report on 2010 through 2015 found that DEP investigated about 230,000 noise complaints and issued fewer than 6,000 violations, while the NYPD investigated 1.3 million and made 791 arrests and 5,482 summonses.²⁷⁷ A 2017 state audit of nightlife noise found that for 85 percent of NYPD responses, either no action was taken or the records did not show how police responded.²⁷⁸

In Boston

Boston sends different noise to different offices - police for parties and car alarms, Inspectional Services for construction, Massport for aircraft, the Public Health Commission for HVAC equipment.¹¹⁵ The full routing table is in The sound of Boston.

Elsewhere in the world: what happens after you complain?

In England and Wales, councils have a legal duty to reasonably investigate complaints of possible statutory nuisance,⁷⁷ but each council sets its own service level, including whether officers come out at night.⁷⁰ If an officer confirms a statutory nuisance, the council must serve an abatement notice.⁷⁰ In the EU, the public must be informed and consulted on noise action plans,²⁵ which is the moment to raise a road or rail corridor that the maps show as loud.

How do people find or make quiet?

What you hear: the drop when you turn off a main road onto a side street, or step into a courtyard.

Distance. Sound from a single source such as a horn falls about 6 dB per doubling of distance. A busy highway acts as a line of sources and falls only about 3 dB per doubling,⁵ or about 4.5 dB over soft ground.⁹ The Federal Highway Administration says traffic noise is usually not serious beyond about 150 m (500 ft) from heavy freeways, or 30 to 60 m (100 to 200 ft) from lightly traveled roads.⁹

Something solid in the way. A barrier that barely breaks the line of sight cuts about 5 dB(A); a good one approaches 10 dB(A). A row of buildings gives about 3 dB(A), plus about 1.5 dB(A) for each additional row. A dense belt of vegetation 5 m tall and 30 m deep can give up to 5 dB(A).⁵ A 10 dB cut sounds roughly half as loud.⁵ This is why a room on the far side of a building, or a street one block back from an arterial, can be noticeably calmer.

Heavy walls, and the bass problem. Walls block sound mostly by mass: transmission loss rises about 6 dB for each doubling of a wall's mass, and falls about 6 dB for each halving of frequency, so bass gets through far more easily than voices. Typical drywall walls also have a resonance dip around 50 to 100 Hz that the standard STC rating can miss. Door seals help with speech, not bass.⁸

Timing. Knowing your local quiet hours tells you when the rules are on your side - for example, power and garden tools are barred in New South Wales from 8 p.m. on weekdays.⁶⁸

Protected quiet. Alongside their action plans, EU member states must select and preserve quiet areas of good acoustic quality.^{76 25} The idea of soundscape - defined in ISO 12913-1 (2014) as the acoustic environment "as perceived or experienced and/or understood by a person or people, in context" - shifts the question from how to remove noise to which sounds are worth keeping.⁹³ Quiet-area mapping and certified quiet parks are covered in Birds, bugs and soundscapes.

Report an error in this section