December 7, 2015

Sound Meter Pro (v2.5) manual

Hello. I'm android boy, the chief developer of Smart Tools co,.

Sound Meter Pro is the 4th set of the Smart Tools suite. It includes 2 tools (sound meter, vibrometer).

※ Introduction video

Ⅰ. Sound Meter
This tool is using your built-in microphone so as to measure sound pressure, and shows a reference. It can be called as SPL (sound pressure level) meter.
① Menu
② Statistic menu (save / load / CSV export)
③ Screen capture

3 Red lines mean max, mean and min values.
④ Refresh : to reset, long-click on the center of meter or click this refresh icon
⑤ Text / Chart toggle

⑥ Black / White toggle : make your screen dim for saving battery
⑦ Play / Pause toggle

 Examples of sound pressure
 20dB : Rustling leaves, Ticking watch
 30dB : Quiet whisper at 3 ft, Library
 40dB : Quiet residential area, Park
 50dB : Quiet office, Quiet street
 60dB : Normal conversation at 3 ft
 70dB : Busy traffic, phone ringtone
 80dB : Busy street, alarm clock
 90dB : Factory machinery at 3 ft
100dB : Subway train, Heavy snoring(2ft)
110dB : Rock music, Screaming child
120dB : Threshold of pain, Thunderclap
130dB : Jet engine at 100 ft
180dB : Space shuttle lift-off

 Don't blame this app for Maximum Limitation
Most microphones are aligned to human voice (300-3400Hz, 40-60dB). It is enough for voice calls. But it occurs an issue of 16 bits microphone limitation.

See sound pressure at calibrate menu. It'll stop at 32767 (32767=2^15-1). In conclusion, 16 bits microphones cannot measure above 96 dB. (more link)

Because of additional optimization (background noise reduction), some devices can measure at most 80 dB. Galaxy S3-S5(81-84db), HTC Desire HD(85db), Galaxy Note(81/91db). Most of Motorola and Amazon devices can measure 96 dB fully.

Last year, a german user suggested a trick in order to bypass hardware limitation. Add +30dB at calibrate menu, and close your microphone hole with your finger, so that you can measure a sound over 100dB. Try it out. :)

 Menu & Settings

 Statistic Menu
① Save : enter title name for current chart
② Load : load the charts stored. To remove a chart, long-click and select [delete] option.

③ Export : export current data as CSV file into SD card. Move it into PC and open with MS-Excel. This function can store up to 24 hours. Here is an example.

 How to calibrate Sound Meter ???
Since 2010, we had calibrated the app on 500+ android devices (major Galaxy, LG, Xperia, Motorola and Nexus). It's a pity that the results were changed easily depending on OS version.

In order to calibrate the app correctly, you must compare it with an ACTUAL sound level meter. Otherwise, ensure that the measured value of a very quiet room is 30-35dB. If the result were out of range, you could add/reduce number at the calibrate menu.

It is an auxiliary tool for reference. Just enjoy it.

 Level Nofitication
A lot of users, especially school teachers, wanted to know if their voices were loud. Turn on [Level Notification] option at the settings.
60dB+ : green, 70dB+ : pink,  80dB+ : red. It is a pity that Sound alarm cannot be used due to amplification.

Ⅱ. Vibration Meter
This tool is using a 3-axis acceleration sensor so as to measure device's vibration, movement or the earthquake, and shows a reference. The value is releated to Modified Mercalli Intensity scale(MMI). It has no unit.
① Menu
② Statistic menu (save / load / CSV export)
③ Screen capture

④ Refresh : to reset, long-click on the center of meter
⑤ Play / Pause toggle
⑥ Alarm : show current alarm situation

 Examples of MMI earthquake scale
  I : Instrumental. Felt by animals
  II : Weak. Felt indoors by a few people
  III : Slight. Felt indoors by several people
  IV : Moderate. Hanging objects swing
  V : Rather Strong. Some dishes broken
  VI : Strong. Heavy furniture moved
  VII : Very Strong. Difficult to stand
  VIII : Destructive. Fall of walls
  IX : Violent. Noticeable cracks in ground
  X : Intense. Almost destroyed
  XI : Extreme. Rails bent greatly
  XII : Cataclysmic. Total destruction

 How to calibrate Vibration meter ???
Most acceleration sensors are unstable and weakened easily, so that calibration is required.

① Go calibrate menu.

② Shake your device as possible as you can. Increase / decrease its sensitivity so that max value reaches about 10-11.
③ Check your unnecessary value measured by no movement.
④ Click [Cut Baseline] button and select an number.

⑤ Repeat ②-④ several times.

Q. It says "Unable to open microphone.".
A. Other app occupied your microphone. Just restart your device.

Q. Where can I find the Screenshot and CSV file?
A. /sdcard/smart-tools/, /storage/sdcard0/smart-tools/, /mnt/sdcard/smart-tools/.

Q. I hear nothing. But the app shows 30-40 dB.
A. A microphone cannot catch very low-frequency noise. 0 dB means the vacuum of space.

Q. Is the result dBA weighted?
A. Yes, I calibrated the app with a actual SPL meter with dBA. But db(A) makes no sense because the result is not perfect.

Q. How to disable tick sound switching from chart to text?
A. Turn off [Sound effect] option at the settings.

Q. What is the unit of vibration?
A. It has no unit, just the scale for reference.

 What's new
 - v2.5.1 : Screen catpure on statistic menu
 - v2.5 : Material design
 - v2.4 : Action Bar
 - v2.3 : Export as CSV file
 - v2.2 : Statistic menu and save log.
 - v2.1 : New icon
 - v2.0 : Sound Meter Pro released (Jan. 2011)

If you have any idea to improve it, feel free to contact me.
Thank you.