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Messages - FaberAST

Pages: 1 2 3 [4] 5 6 ... 22
IOScope / Re: IOScope settings
« on: December 03, 2012, 10:04:25 AM »

To see units other than FS and Pa, please ensure that you are working with an input source other than the built-in microphone.

IOScope does not currently support arbitrary band limits on the built-in frequency sweep (i.e. it is a full bandwidth sweep).


SoundMeter / Re: Logging and exceedances
« on: November 01, 2012, 12:20:20 PM »

These features have not yet been implemented on iOS, but we do plan to offer them in the future.


SignalScope Pro / Re: iPhone HPF
« on: October 30, 2012, 12:23:06 PM »

Please check out this recent post on the blog:

An app has to select the appropriate audio settings in iOS to disable the filter, which our apps do.


SignalScope Pro / Re: Normalize cables and iPhone response
« on: October 30, 2012, 12:12:52 PM »

Since it sounds like your goal is to perform frequency response measurements, I would recommend that you take a look at IOScope, which is a true dual-channel analyzer. It offers frequency response magnitude and phase, group delay, coherence, impulse response and cross-correlation. With IOScope, you could solve your "normalization" concern to a great extent, by measuring the frequency response by connecting the input and output of your DUT to the two input channels on your iU2.

Still, correcting for the response of the I/O path is something that we may add to IOScope in the future (this function already exists in the Mac counterpart, which is the Dual FFT Analyzer in Electroacoustics Toolbox).

Best regards,


IOScope / Re: Block diagrams of I/O
« on: October 30, 2012, 12:04:48 PM »
Do you know of issues with the missing Ch2-Ch1 input option with the Line6 Mobile In and/or iPod touch 5G combination ? 
I have seen that sometimes, the difference channel (Ch2-Ch1) doesn't show up in the input channel list when using the hardware you mentioned (iPod touch 5, Mobile In, Lightning adapter). It should work however, if you restart the app and reconnect the Mobile In. I'm still not sure exactly what the issue is that causes this behavior.

Would using a power amplifier be advisable to take some current load off the iPod/iPhone/iPad headphone output ?
You could use an amplifier. You could also increase the size of your series resistor (8.2 ohms is pretty low).

Are you aware of any iPhone/iPod/iPad compatible USB input devices that have floating inputs ?
Perhaps, you could look for a digital input device and use a separate piece of hardware to handle your analog signals.


IOScope / Re: Block diagrams of I/O
« on: October 29, 2012, 05:38:15 PM »

It's not clear what you are hoping to see in a block diagram. Both channels of the headphone out and the microphone input all share the same common return path on the headset jack.

High voltages are not recommended for the headset jack.


Is there something that I'm missing or is this a bug?
Do you have any of the captured traces checked in the Captured Data Sources list?
In the Display tab of the Controls drawer (at the bottom of the window), is the Draw column checked for the captured traces you are trying to display? Is the vertical scale selection appropriate for the data?

In this case, a screenshot of the Oscilloscope tool in the re-opened project could be helpful, so we can see what you are seeing.



SoundMeter / Re: Accuracy for home night noise measurement
« on: July 30, 2012, 10:22:21 AM »

How accurate reading can I get with SoundMeter after calibration?
If you calibrate at 1 kHz, then you should easily be able to achieve accuracy within 0.1 dB at 1 kHz. You should be aware of the current high-pass filtering applied the iPhone's built-in microphone. This issue is discussed on our blog.

If you need true class compliance, then you'll need a dedicated sound level meter build for that purpose. MicW makes a microphone that plugs into the headset jack that they claim conforms to standards for Type 2 sound level meters. However, the iPhone's headset input also passes through the high-pass filter.

We're hopeful that Apple will provide developers with a means to bypass the mic input filter, but we won't know for sure unless/until it happens.


SignalScope Pro / Re: which internal microphone?
« on: July 06, 2012, 01:38:52 PM »
SignalScope uses the main microphone, which is situated at the bottom of the iPhone 4. SignalScope cannot use both internal microphones at the same time.

SignalScope / MOVED: Mic Pre Amp fo iPhone 4s
« on: June 27, 2012, 04:57:35 PM »

Electroacoustics Toolbox / Re: Calibration settings mics
« on: May 18, 2012, 10:42:22 AM »
Electroacoustics Toolbox does not support external microphone frequency response correction curves. However, since you have this data, you could use it to correct 1/3-octave measurements manually or export measurement data and correct it within a spreadsheet.

Sensitivity calibration will still require that you use a calibrator or another calibrated instrument.


SignalScope / Re: Is white noise output flat across range?
« on: May 07, 2012, 09:31:00 AM »

A. You cannot generally expect white noise to be white anymore after it passes through a loudspeaker.
B. The acoustic environment (room) in which the loudspeaker is placed further affects the signal.
C. It is important to understand that white noise with a similar level to a single tone will have it's energy distributed across all frequencies. This means that the level at each frequency is much lower than the level of the single tone.


SignalScope / Re: Is white noise output flat across range?
« on: May 03, 2012, 09:00:20 AM »

How are you generating the white noise signal? Have you purchased the signal generator upgrade in SignalScope?

How are you measuring the spectrum of the white noise signal? Which input is the white noise connected to you your iOS device?


SignalScope / Re: Signal Generator output on an analog oscilloscope
« on: April 23, 2012, 04:56:24 PM »

First, it should be noted that this post pertains to the signal generator tool in SignalScope (available via in-app purchase), which is not the same as SignalSuite. This is why this post was moved from the SignalSuite forum to the SignalScope forum.

I'm puzzled, though, why the overall waveform rises as frequency rises. I can't understand where that rising DC offset would come from.
The rise is due to the low-frequency "tail" wrapping around into the high frequency part of the sweep (it's not a DC offset). This happens because the sweep is synthesized in the frequency domain and converted to a time-domain signal via inverse FFT.

Also, does the tapering look right to you--3 db/oct. seems to take a long time to kick in and then it does with a vengeance at the end...is that to be expected with a logarithmic sweep?
"Logarithmic sweep" means that the frequency increases logarithmically, so the frequency increases more rapidly toward the end of the sweep. A -3 dB per octave slope in the frequency domain basically means that the sweep spends more time at lower frequencies and less time at higher frequencies.

Finally, the doc says that the high and low frequency limits for the sweep depend on the settings of the FFT portion of the suite, but no matter where I set the high frequency limit in that app, the sweep seems to run the same range. Am I missing something?
The lower frequency bound of the sweep is always 0 Hz (or something close to that, in the case of a log sweep). The upper frequency bound is determined by the sample rate of the audio input signal. The upper frequency limit is half the sample rate, which is typically 48 kHz, although some devices only sample at 44.1 kHz. You cannot manually change the sample rate within SignalScope.
Perhaps, you are referring to the sweep duration, which is tied to the length of the FFT in the FFT analyzer. Increasing the frequency resolution of the FFT analyzer (selecting a smaller value, in Hz) will also increase the duration of the sweep.


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