Comparison

Decibel X vs SPL Reference

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Decibel X

This tool transforms your device into a professional sound level meter, offering precise measurements of ambient noise. It features advanced calibration, frequency analysis, and data management for various applications, from personal curiosity to professional use.

Highlights
  • Pre-calibrated sound pressure level (SPL) measurements
  • Frequency weighting filters (dBA, dBC, ITU-R 468)
  • Apple Watch and Health App integration
  • History data management with export options
  • Dosimeter with NIOSH, OSHA standards
  • FFT and BAR graphs for real-time frequency analysis
  • InstaDecibel for sharing dB reports on photos
Features
Read full description

"Decibel X" is one of very few noise meter apps on the market that has highly reliable, pre-calibrated measurements and supports dBA, dBC. It turns your iOS device into a professional sound level meter, precisely measures the sound pressure level (SPL) all around you. This extremely useful and beautiful tool will not only be a great tool for many uses but also bring you a lot of fun. Have you wondered how quiet is your room or how loud is a rock concert or sport event? "Decibel X" will help you answer all of those. WHAT MAKE IT GREAT AND STAND OUT FROM OTHER APPS: - Trusted accuracy: the app is tested and pre calibrated for all Apple devices. The precision is matching with real SPL devices - Apple Watch support: see noise level right from your wrist - Health App integration: export noise levels directly into Health app - Frequency weighting filters: ITU-R 468, A, B, C, Z - Powerful, smart history data management: + Recording data can be saved into a list of history records for future access and analysis + Each record can be exported as hi-res PNG graph or CSV text via sharing services + iCloud support which synchronize all history records across your Apple devices + Fullscreen mode to give overview the whole history of an record - Dosimeter with NIOSH, OSHA standards - Powerful calibration: Linear, Octave 1/1, 1/3, Load/save profile - FFT and BAR graphs to display real time FFT. Those are very useful for frequency analysis and musical tests. Real time predominant frequency is also displayed. - InstaDecibel to capture your dB report overlaid on photos and easily shared via popular social networks (Facebook, Instagram, Messages, etc.). - Support Live Activity, Dynamic Island - Support both Portrait and Landscape layouts - Beautiful, intuitive and carefully crafted UI design. Themes: LIGHT, DARK and CLASSIC OTHER GREAT FEATURES: - Standard time weightings (Response Time): SLOW (500 milliseconds), FAST (200 milliseconds) AND IMPULSE (50 milliseconds) - MIC Gain Offset from -50 dB to 50 dB - Standard measurement range from 30 dBA up to 130 dBA - HISTO graph for plotted history of the recorded values - WAVE graph with 2 display modes: Rolling & Buffer - SPECTROGRAPH - Real time scale level chart - Display Current, Average/Leq, and Max values with both nice and clear digital and analog layouts - Quick reference text to help you compare with real-life examples NOTES: - Please do not expect a quiet room reading will be 0 dBA. The range 30-130 dBA is the standard usable range and an average quiet room will be about 30 dBA. - Although all devices are pre-calibrated, custom calibration is suggested for serious purposes requiring higher precision and accuracy. You will need a real external device or calibrated sound meter as a reference, then adjust the trimming calibration until the reading matches with the reference. * Privacy Policy: http://www.skypaw.com/decibelx/privacy_policy.html * EULA: http://www.skypaw.com/decibelx/terms.html

About

SPL Reference

Read full description

Hear your system. See your room. SPL Reference combines sound-level measurement with Room Map, a new way for Hi-Fi enthusiasts to explore how bass changes across a listening room. Measure at several positions and see areas of relatively high and low sound pressure at the selected frequency, helping you investigate uneven bass and make more informed speaker and listening-position choices. EXPLORE YOUR LISTENING ROOM • Create a rectangular room and follow a guided 9- or 12-point survey, or customise your measurement positions. • Explore frequency-selectable heatmaps with 1/12- or 1/3-octave bands. • Use generated bass pink noise through your playback system, or a stable external pink-noise source. • Review individual points, capture-quality notes and a repeat measurement at the reference position. • Save maps in Sessions, organise them in projects and export the survey data. A COMPANION TO ROOM REFERENCE Use SPL Reference alongside the separately available Room Reference app to add measured spatial bass comparisons to your room investigation. We are working to integrate the two apps; direct integration is not included in this release. MEASURE WITH CONTEXT • Live A-, C- and Z-weighted measurements • Fast, Slow and Impulse time responses • LAeq, LAFmax, LCpeak and time-history views • Pause, resume, event markers and integrity evidence • Clear distinction between indicative readings and reference-calibrated chains ANALYSE AND DOCUMENT • 1/1- and 1/3-octave frequency analysis, spectrum and spectrogram history • Statistical exceedance levels from L1 to L99 • Noise-exposure assessment using NIOSH, OSHA and configurable models • Projects, notes, photographs and optional location evidence • Microphone profiles, acoustic calibration records and drift checks • Professional PDF reports for ordinary sound-level measurements Browse the public measurement archive from inside the app. Measurements are never uploaded automatically. START FREE. UPGRADE ONCE. The free tier includes the built-in microphone, five active measurement minutes per calendar month, two saved measurements and one project. Room Map and advanced features require Lifetime Professional Unlock, which removes the free limits with one purchase and no subscription. Room Map is included for existing Lifetime Professional owners. ABOUT YOUR RESULTS Room maps show the combined response of your speakers and room at one microphone height. Colours compare the selected frequency across measured positions. Uncalibrated maps display relative levels in dBFS. Results depend on the microphone, calibration, playback setup and measurement conditions. SPL Reference distinguishes indicative and calibrated workflows and does not claim that an unvalidated device is a certified sound-level meter. Occupational-noise results support assessment and documentation; they do not replace professional judgement or applicable legal requirements.

Screenshots

Decibel X4 screens
SPL Reference4 screens

Verdict

The call

The clearest difference is update cadence: SPL Reference at every 2 weeks against Decibel X's every 3 months. Decibel X's advantage is device support (3 vs 1). On price, ads, in-app purchases and iOS requirement there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Decibel X sells 5 in-app purchases, starting at $1.99 per 7 days and SPL Reference sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

UpkeepUpdate frequency

Decibel X ships an update every 3 months, SPL Reference every 2 weeks. The most recent releases landed on November 10, 2026 and October 31, 2026 respectively.

Scorecard2 real differences · 8 level
Decibel X versus SPL Reference: the parameters behind the verdict, then further details
ParameterDecibel XSPL Reference
PriceFreeFree
Rating4.6 (164K ratings) — better—
Positive reviews66.3% of reviews—
Number of ratings164K — better—
Update frequencyEvery 3 monthsEvery 2 weeks — better
AdsNoNo
In-app purchasesYesYes
MonetizationFreemium—
DevicesiPhone, iPad, Apple Watch — betteriPhone
Requires iOS17.017.0
Further details — not scored
Size90 MB6 MB
Age rating4+17+
DeveloperSkyPaw Co., LimitedDirect Sound Records Ltd

Bugs and requests

Decibel X

Reported bugs

3 issues
  • App crashes when deleting recordings
  • Microphone issues on certain devices
  • Saved files not accessible after updates

Requested features

5 requests
  • Add GPS coordinates to recordings
  • Improve reporting and data export
  • Provide more weighting options
  • Extend frequency range
  • Allow music playback while using the app

SPL Reference

Not enough reviews yet to summarise bugs or requests.

In-app purchases

5 purchases

Decibel X

Subscriptions3
  • Weekly Membership$1.997 Days
  • Monthly Membership$5.991 Month
  • Annual Membership3 Days trial$49.991 Year
One-time2
  • ITU-R 468, A, B, C Weightings$1.99
  • Data Export$2.99
1 purchases

SPL Reference

One-time1
  • Lifetime Professional Unlock$39.99

Questions

Is Decibel X free?
Decibel X is free to download, with in-app purchases available.
Is SPL Reference free?
SPL Reference is free to download, with in-app purchases available.
Do Decibel X or SPL Reference have ads?
Neither Decibel X nor SPL Reference shows ads.
Which is updated more often, Decibel X or SPL Reference?
Decibel X ships an update every 3 months, and SPL Reference every 2 weeks. Most recently, Decibel X was updated on November 10, 2026 and SPL Reference on October 31, 2026.

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