How to Use Decibel X (Free Version) to Record Construction Noise

Decibel X is one of the most accurate sound level meter apps available for smartphones, and the free version provides all the key features you need to document construction noise effectively. This guide walks you through everything from setup to evidence export.

What is Decibel X?

Decibel X (also listed as dB Meter Pro or DecibelX on some app stores) transforms your phone's microphone into a professional-grade sound level meter. It uses your device's built-in microphone to give real-time dB readings and display averaged and peak levels.

Download links:

• iOS (iPhone/iPad): Search "Decibel X" on the App Store — look for the app by SkyPaw Co. Ltd
• Android: Search "Decibel X" on Google Play Store

The free version is fully functional for noise complaint purposes. A paid "Pro" version adds additional logging features, but you do not need it.

Step 1: Setting Up the App

When you first open Decibel X:

1. Grant microphone permission – the app will ask to access your microphone; tap Allow
2. Choose the correct weighting – set to dB(A) weighting. This is the standard used in UK legislation and is what Environmental Health Officers use. Look for "A" or "dBA" in the app settings or on the main screen
3. Set the response time to Slow or Fast – for construction noise, use Slow as it smooths out brief spikes and gives a more representative reading
4. Check calibration – in a quiet room, your reading should show approximately 30–40 dB. If it shows significantly higher in silence, your phone's microphone may be picking up wind noise

Step 2: Understanding the Display

The main screen shows several key values:

• Current dB level – the large number in the centre, updating in real time
• MAX – the highest peak recorded during your current session
• MIN – the lowest level recorded
• AVG – the average level over the measurement period. This corresponds to the LAeq value used in UK legal assessments and is your most important figure

The AVG/LAeq value is what matters most for UK noise complaints. Councils and courts assess construction noise against LAeq thresholds, not momentary peaks.

Step 3: Taking a Measurement

For your evidence to be meaningful, follow this process:

Positioning

• Hold your phone at arm's length pointing towards the noise source
• Do not cup your hand around the phone — this affects the microphone
• Avoid holding the phone close to your body, which can cause reflections
• If measuring indoors, stand close to (but not directly in front of) an open window

Duration

• Record for at least 60 seconds to capture a reliable average
• For intermittent noise (e.g. drilling that starts and stops), try to capture at least two full cycles of the loudest activity
• For a more formal complaint, aim for 5–10 minutes of recording to capture the true sustained level

Multiple Locations

Take readings from at least three positions:

1. Inside your home (living room or bedroom — whichever is most affected)
2. At your front door or doorstep
3. At the boundary of your property closest to the noise source

Record the AVG reading at each position, along with the time and your exact location.

Step 4: Capturing Evidence

Taking a Screenshot

After your measurement period:

1. Press the pause button to freeze the readings
2. Note down the AVG, MAX, and MIN values displayed
3. Take a screenshot of the screen (press and hold the power + volume button on most phones)
4. The screenshot will include the readings and, importantly, your phone's timestamp visible in the notification bar

Using the History / Log Feature

In the free version, you can access a basic session history. After each measurement:

• Note the reading in your own written log alongside the date, time, address, and type of noise
• This written log, combined with your screenshots, forms a strong evidence pack

Step 5: What the Numbers Mean

Use this reference table when interpreting your AVG readings:

Note: These thresholds apply to daytime hours (07:00–23:00). At night, limits are far lower — typically 45 dB — so even moderate readings during night hours can support a complaint.

Step 6: Wind and Environmental Interference

Wind is the most common cause of inaccurate smartphone readings. If it is windy:

• Shield the phone microphone with your hand or body (without covering it completely)
• Note the weather conditions in your written log
• Consider taking readings on a calmer day for comparison

Other sources of interference to note:

• Traffic passing close by — note if a vehicle passed during the reading
• Aircraft — pause and restart if a plane flies over
• Rain — avoid outdoor measurements in rain where possible

Step 7: Exporting and Sharing Your Evidence

In the free version, your primary evidence will be screenshots. To organise and share them:

1. Create a dedicated folder on your phone called "Noise Evidence"
2. Save all screenshots there, keeping filenames or notes with the date and location
3. When writing to your council or Environmental Health team, attach screenshots as image files to your email
4. Reference the readings explicitly in your letter: e.g. "On 15 March at 09:30, I recorded an average LAeq of 78 dB at the boundary of my property at [address]."

Tips for Court-Ready Evidence

If your complaint escalates to a magistrates' court under Section 82 of the Environmental Protection Act 1990, stronger evidence helps. To make your Decibel X recordings as credible as possible:

• Record consistently — same positions, same app settings, multiple dates
• Accompany readings with a written log — date, time, weather, description of the noise, and your reading
• Take video on a second device simultaneously if possible, so the noise and the app screen are captured together
• Note the phone model — some models are more accurate than others; courts may ask
• Keep raw screenshots unedited — do not crop or alter the images

Limitations of Smartphone Measurements

While Decibel X is highly regarded, it is worth noting:

• Smartphone microphones are not Type 1 or Type 2 calibrated instruments as defined by IEC 61672. Courts and councils may treat readings as indicative rather than conclusive
• For the strongest evidence, consider hiring a professional noise consultant to take calibrated readings if your complaint is serious
• That said, consistent smartphone readings from multiple sessions significantly strengthen a complaint and are widely accepted as supporting evidence by Environmental Health Officers across the UK