FAQ-E014: What is the background noise? Its influence?

FAQ-E014: What is the background noise? Its influence?

The background noise is a sound that exists in a certain place other than the target sound when considering a specific sound.

In the case of measuring the noise level of a specific steady noise, it may be affected by the background noise.

When measuring the noise level, if the difference between the indicated value of the sound level meter with and without the noise is 10 dB or more, the influence of the background noise can be almost ignored.

However, when it is less than 10 dB, it cannot be ignored, and the noise level of only steady noise can be estimated by correcting the following table.
Note that this correction is for stationary noise and cannot be applied when the background noise level fluctuates. The difference from the background noise level must be at least 3 dB.
# Measurement value difference : Correction value (unit: dB)
     3         : -3.0
     4         : -2.3
     5         : -1.7
     6         : -1.25
     7         : -0.95
     8         : -0.75
     9         : -0.60
    10          : -0.45

* Note: ISO 1996-1 (JIS Z 8731: 1999 “Description and measurement of environmental noise”)

For example, if a certain machine is measured to be 55 dBA and the background noise when it is stopped is measured to be 50 dBA. Since the level difference is 5 dB, the level is estimated to be 53.3 dBA.

* Applicable apps :
- Sound Level Analyzer PRO
- Sound Level Analyzer
- Sound Level Analyzer Lite - Free of charge!
posted by toons at 19:53 | FAQ


FAQ-A013 : What is "Octave Band Noise"?

FAQ-A013 : What is "Octave Band Noise"?

[Answer] "Octave Band Noise" is a noise signal that extracts only energy of a bandwidth of a certain one octave frequency with respect to white noise and pink noise.

The noise signal can be used for various purposes as a reference sound source for environmental sound measurement, sound tuning, auditory effects like tinnitus relief and sound masking.

Our app "Colored Noise Generator" provides an octave band noise can be output programmably.

cng_white_oct_v300.jpg cng_pink_oct_v300.jpg

I will explain "Octave Band Noise" in more detail. An octave is a pitch that doubles the ratio of frequencies to a certain frequency. And the octave band is the bandwidth of the frequency where the ratio of the upper and lower frequencies centered on a certain frequency is exactly one octave. The center frequency of this octave band is called the center frequency, and the frequency band for the center frequency fo ranges from the lower limit frequency fo/√ 2 to the upper limit frequency fo*√2. For example, the center frequency of an octave band is 1 kHz, 2 kHz, 4 kHz ,,,, and one octave is divided into three in the 1/3 octave band.

"Octave Band Noise" is a noise signal that extracts only a specific frequency band with the band-pass filter with the octave band characteristics. Using the noise, it is possible to evaluate only the target frequency band. By measuring the pink noise of a specific frequency band with a real-time analyzer, it is possible to make sound adjustments and measure noise source characteristics that are not affected by other frequency bands.

The figure below shows an example of generating 1/1 octave band noise at the center frequency (1000 Hz and 4000 Hz) with white noise as the source signal. It is FFT analysis result by our audio analyzer app "Audio Frequency Analyzer". Since this measurement result is an instant observation value, it can obtain a flat frequency characteristic within the octave band in time averaging.

posted by toons at 23:57 | FAQ


FAQ-S012 : Let me know the iOS device reset method.

[Answer] It depends by the iOS devices how to reset/restart.
Please refer to the following Apple support page.


posted by toons at 09:43 | FAQ

FAQ-S011 : The installed app quits unexpectedly, it stops responding, or does not start up.

[Answer] Depending on the operating status of the iOS device, free memory, operation settings, conflicts with other applications and etc., the app might suddenly end, or may not respond, or may not start up. In that case, please try the following methods.

1) Restart the app.
2) Restart your device.
3) Check for iOS and app updates.
4) Install another app from the App Store.
5) Delete and reinstall the app.

# Please refer to the following Apple support page for this solution.

posted by toons at 09:34 | FAQ

FAQ-S010 : The app can not be successfully downloaded.

[Answer] Depending on the operating status or the communication status of iOS device, the app may not be downloaded successfully.
There may be a phenomenon that the icon remains downloading or you can not run the app even though the downloading is completed. In that case, please download the app again.

- Open App Store.
- Open the App Store app.
- On an iPhone : Tap Updates, then tap Purchased.
- On an iPad: Tap Purchased.
- Tap "Not on This [device]."
- Find the app that you want to download, then tap download icon. The app downloads to your device.

# Please refer to the following Apple support page for this solution.

posted by toons at 09:30 | FAQ


FAQ-E009 : During the measurement of "Low Frequency Detector" app, the reference tone signal is output, but is this operation normal?

[Answer] Yes, it is normal operation.
”Low Frequency Detector” app measures the sound level of the very low frequency band below 100 Hz.
The reference tone signal (1kHz) is output from the built-in speaker during the low-frequency sound level measurement. This app collects both the reference tone signal and the ambient sound at the same time, and analyzes the collected sound data to detect its low frequency component. The detection level is a relative level to the reference tone signal. Therefore, please be sure to set the playback level and calibration at the first boot.

Target app : Low Frequency Detector

posted by toons at 23:56 | FAQ


FAQ-E008 : What is the maximum frequency that can be measured with "Vibroscope"?

[Answer] In "Vibroscope" app, the data sampling frequency from the sensor device is displayed at Fast 100 Hz and Slow 30 Hz. It depends on the specification of the sensor device currently installed in the iPhone, so the sampling frequency is maximum 100Hz (10ms). In FFT display, the measurent frequency up to 1/2 of the sampling frequency are analyzed and displayed. In addition, the log data are saved at 10 ms intervals in both LOW and FAST.

Target application: Vibroscope

posted by toons at 21:14 | FAQ


FAQ-A007 : How should I connect iPhone/iPad to the audio system in a signal generation app?

FAQ-A007 : How should I connect iPhone/iPad to the audio system in a signal generation app like "Audio Tone Generator" ?

[Answer] Audio signal generation application can connect to audio system by the following method.
(1) Output from 3.5mm headphone jack.
(2) Output using Lightning compatible digital audio interface.
(3) Connect with AirPlay using WiFi.

We recommend to use the Lightning' connection in (2) since the digital audio output has the highest signal accuracy and is stable as the reference signal source.
In addition, AirPlay in (3) has sound quality problems in the receiving equipment since it adopted Apple's proprietary wireless communication method. It seems to occur by wireless communication status, compatibility with connected equipment, and audio data compression algorithm. According to our user report, there is information that the sound via AirPlay may be interrupted momentarily the audio signal in the higher frequency band of over 10 kHz in the sinusoidal frequency sweep.

Applicable App : Audio Tone Generator, Audio Tone Generator Lite, Audio Tone Generator for iPad, Octave Band Noise Generator/Lite

posted by toons at 21:34 | FAQ


FAQ-E006 : How to get the log data of "Vibroscope".

FAQ-E006 : How to get the log data of "Vibroscope".

[Answer] In "Vibroscope" measurement data and time information are saved in iPhone as log data (text format). This log data can be imported to PC by iTunes file sharing.

- Connect the PC and iPhone with a USB cable.
- Import log data from iTunes file sharing to PC.
For more information on iTunes file sharing, please refer to Apple's official support site.
- iTunes file sharing : https://support.apple.com/en-us/HT201301

Applicable app : "Vibroscope"

posted by toons at 18:45 | FAQ


FAQ-A005 : Is it possible to input the microphone from the earphone jack? Frequency characteristics? (Fo-Kannon)

FAQ-A005 : Is it possible to input the microphone from the earphone jack? Frequency characteristics? (Fo-Kannon)

[Answer] In "fo-Kannon", we have received some inquiries about microphone input from iPad's 3.5 mm earphone jack.
We measured characteristics of our own microphone (SONY ECM-959V : sorry for a bit of an old microphone). Pink noise is reproduced from the speaker and it is measured by holding at the position of about 1 m in front of the speaker for 5 seconds. It was confirmed that the low frequency gently decayed.
This is an example of measurement result including our loudspeaker's frequency response but it seems that it will not be a ridiculous characteristic even if it is a type of microphone inserted in the earphone jack. However, please note that the results will change depending on the characteristics and the impedance matching of your using microphone.

Applicable app : "fo-Kannon"


posted by toons at 19:57 | FAQ