Click on the text links below to read each question and its
answer.
Q: Why Smaart?
A: Since the release of SIA-SmaartŪ version 1.0 (formerly
marketed by JBL Professional as "JBL-Smaart") in 1996, SIA Smaart software
products have become some of the most widely used audio/acoustic measurement and analysis
tools in the world. The SIA SmaartLive and Smaart Acoustic Tools feature sets are the result
of careful listening to our users and continual development. Our goal is simple: to provide
truly exceptional value and support to our users and to build the most powerful, flexible,
cost-effective and usable tools for acoustic measurement and sound system
optimization and control available anywhere.
Q: What are some of the most
important capabilities of SIA SmaartLive?
A: SIA SmaartLive offers the functionality of a dual-FFT real-time
transfer function analyzer as well as a standard FFT-based real-time spectrum analyzer
(RTA) entirely implemented in software. The Transfer Function display provides a
frequency-domain comparison of two signals yielding precise frequency (magnitude and
phase) response for the device or system under test in real-time. This is an extremely
powerful tool for assessing the performance of an entire sound system, a specific part of
a system, or a single system component. Additionally, this dual-channel measurement
technique is "stimulus-independent," meaning that it works with a wide variety
of signal types, including music as a test signal.
Utilizing another variant of the dual-channel transfer function
technique SmaartLive can produce very precise and repeatable impulse response
measurements, useful for acoustical analysis, and measure delay times with resolution
approaching 2/100 milliseconds. This high degree of precision makes SmaartLive an
excellent tool for aligning multi-driver loudspeaker systems, loudspeaker arrays, and
distributed sound systems. Impulse response measurements in SmaartLive can be stored as a
standard Windows wave file making the data fully compatible with Smaart Acoustic Tools.
In addition to it's time- and frequency-domain measurement
capabilities SmaartLive can also be used remotely control a growing list of third-party
equalizers, system processors, and other devices. This capability greatly streamlines the
process of sound system setup and optimization by allowing you to measure, analyze and
control sound system performance and parameters from a single application.
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Q: What are some of the
important capabilities of SIA Smaart Acoustic Tools?
The Smaart Acoustic Tools package consists of two application
modules; Analysis and Intelligibility. Below are some of the most important features of
each program.
The Analysis Module:
The Smaart Analysis module reads audio data stored in any standard
Windows wave (*.wav) file including impulse response files recorded in the Intelligibility
module or SmaartLive. The Analysis module can open one or two wave files at a time and can
transform time-domain data in the wave file(s) into its frequency domain representation,
using a series of Fast Fourier Transform (FFT) calculations. Both time and frequency
characteristics of recorded signals can then be displayed, compared and analyzed a number
of ways.
The Analysis module is primarily designed for use in analyzing
impulse response data and includes tools to help you find reflections, reverberation and
decay information and early-to-late energy ratios. Other possible uses for this program
include speech analysis or any application where you need to analyze the time and
frequency characteristics of recorded signals.
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The Intelligibility Module:
Like the Analysis module, the Smaart Intelligibility module is
primarily designed for analyzing impulse response data. As the name implies, the
Intelligibility module allows you to calculate several objective measures of speech
intelligibility including %ALCons, Clarity, STI and RSTI, and several quantitative
acoustical values, all from a single impulse response measurement. The program includes an
internal impulse response recorder that can measure the impulse response of a room/system
using either a Maximum Length Sequence (MLS) technique or the same dual-channel transfer
function technique used in SmaartLive to measure delay times.
The Intelligibility module also uses a standard Windows wave file
as its native data file format, allowing you to analyze data acquired through SmaartLive
or virtually any other source. Unlike the Analysis module, the Intelligibility module
operates entirely in the time domain. In addition to the standard time vs. amplitude
display, the program can display the result of Schroeder Reverse Time Integration and
Energy Time Curve (ETC) calculations based on the same wave file data. The Intelligibility
module can also filter and display the raw time-domain wave file data in octave and
1/3-octave passbands "on the fly" and can write filtered data to new wave files
for use in other applications.
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Q: Can you really make accurate
measurements using off-the-shelf and/or built-in computer sound hardware?
A: Yes! There are two main reasons for this. The first is that
SIA-Smaart uses only the Analog-to-Digital section of the computer's sound hardware. The
16-bit A/D converters used in even inexpensive and/or built-in computer sound hardware
today are really better than you might imagine in most cases. The second reason has to do
with the nature of the dual-FFT transfer function measurement technique used for both
real-time frequency response (SmaartLive) and impulse response/delay measurements
(SmaartLive and Smaart Acoustic Tools).
Because both the reference (stimulus) and measurement (system
response) signals in a dual-channel transfer function measurement travel through the same
components as they enter the measurement system (the computer) and the object of this
exercise is to find the difference between the two signals, many imperfections in
the computer’s audio input section will tend to "cancel out" of the
measurement almost entirely. We have performed a number of head-to-head tests comparing
our software (using off-the-shelf sound hardware) with precision audio analyzers and
dedicated hardware/software measurement systems costing tens of thousands of dollars. In
every case, the differences in measured results have been extremely small across the
entire audio spectrum.
Notes:
We do recommend that you use only the Line level inputs on off-the
shelf computer hardware. The analog preamp circuitry used on the microphone inputs rarely
approaches the quality needed for professional measurement applications.
It should be noted that the MLS measurement option in the
Intelligibility module (included in Smaart Acoustic Tools, see above) may tend not to
be as forgiving of the computer's audio section as the dual-channel transfer function
technique. When using a single-channel (stimulus-dependent) measurement technique such as
MLS, it is unavoidable that part of what you end up measuring is the measurement system
itself and it becomes much more vital that both the input and output stages be as clean
and transparent as possible.
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Q: What external hardware is
required for use with SmaartLive and Smaart Acoustic Tools?
A: To use SmaartLive effectively and/or perform impulse response
measurements using Smaart Acoustic Tools, you will probably need a few pieces of outboard
equipment. A typical Smaart measurement will include some combination of the following:
1) A measurement microphone. This should be a high-quality
omnidirectional with very flat response across the audio spectrum -- or at least across
the frequency range you need to measure. There are a number of microphones available from
Earthworks, Josephson, and others in the $400 - $500 (USD) price range that are excellent for
use with Smaart. And depending on your application, you might be able to
get along with an even less expensive microphone. For example, you may not necessarily
need a microphone that is flat all the way to 20kHz if the system you want to measure only
goes up to 15kHz. If you have a high-quality SPL meter available with an audio (AC)
output, this can also work well as a measurement microphone.
2) A small mixer of some kind is typically used to provide level
control to the computer, and preamplification and phantom power for the microphone(s) in a
Smaart measurement system. Using a mixer will also allow you to switch between multiple
measurement points in a system easily without repatching cables. We recommend that you
look for a mixer with channel mute switches so that once the input levels from various
sources have been matched, you can simply turn the signals on and off when switching
between measurement points.
3) A signal source. An internal signal generator is provided in
both SmaartLive and the Intelligibility module in Smaart Acoustic Tools. Note, however,
that the computer can only be used as a signal source if the sound hardware is capable of
full-duplex operation (playing and recording simultaneously) and it may still be desirable
to have an external signal source available in many cases. The best value for an external
signal source is probably a portable CD player and a reference disk with a pink noise
track. You may also want to invest in (or build) an inexpensive pink noise generator. You
may want to have a CD player on hand in any case as this will allow you to use music for
the final stages of setting up a system with SmaartLive. When selecting a CD player try to
find a model with a repeat function so that you can play specific tracks more or less
continually.
4) Y cables and adapters. These are used for patching the
measurement system into various points in the signal path of a sound system —
typically across system EQs. Using Y-cables to split the signal allows you to take the
output from a number of points along the signal chain without interrupting the operation
of the system while you re-patch cables and to "A/B" between various measurement
points easily.
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Q: Can SmaartLive compensate for
irregularities in the frequency response of inexpensive microphones?
A: The short answer is "no." We recommend that you use a
very flat, well-behaved, omnidirectional microphone when performing measurements with
Smaart Pro. There are several on the market for under $600 (USD).
The long answer is that while it would be a fairly easy to do
simple magnitude compensation for single-channel RTA mode measurements, attempts to
compensate for microphone response in more complex operations (such as real-time Transfer
Function and impulse/delay measurements) would almost certainly introduce more errors than
were "corrected." The reason for this is that the "dips and peaks" in
the frequency response of lesser quality microphones vary widely with angle (pitch and
yaw) and are the result of frequency dependent delays (i.e., phase response problems). To
correct for this would require complete complex spherical response data for each
microphone on a unit-by-unit basis. And even if the necessary data were available, the
sheer number of calculations you would need to perform in real time would require much
more processing power than PCs can now provide.
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Q: Do SmaartLive and Smaart
Acoustic Tools generate any kind of stimulus signal?
A: Yes. SmaartLive can generate several types of pseudo-random noise,
variable-frequency single and dual sine wave, and FFT-synchronized, logarithmically swept
sine wave signals. Additionally, any standard wave file may be looped continuously, allowing
users to create their own test signals. The Intelligibility module
in Smaart Acoustic Tools provides a pink noise generator and a wave file loop option for
use in dual-FFT impulse response measurements and an MLS generator for MLS measurements.
Note that to use the computer as a signal source for measurements, your sound hardware must
be capable of full-duplex operation (playing and recording simultaneously). Most newer sound
hardware does have this capability however some older devices may not.
Keep in mind, that SmaartLive is a stimulus-independent
measurement system and allows you to make measurements using a wide variety of test
signals. Use of the internal signal generator is entirely optional and depending on your
measurement application, you may still want to keep an external signal source such as a CD
player on hand. For sound system optimization, particularly in the final stages of system
setup when qualitative judgements are required, it is often desirable to use recognizable
program material (e.g., music) as a test signal, thereby making your own ears part of your
measurement system (as they always should be). The dual-FFT transfer function impulse
measurement option in the Intelligibility module is also stimulus-independent however pink
noise is typically the test signal of choice for most acoustic measurement applications.
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Q: What types of test signals
do you recommend for measurements?
A: Most measurements in both SmaartLive and Smaart Acoustic Tools
are stimulus-independent and will work with a wide variety of internally or externally
generated test signals. The exception is that MLS measurements in the Smaart Acoustic
Tools Intelligibility module require the use of the program's internal MLS signal
generator.
Random or pseudo-random noise is often the best choice for a test signal in
initial stages of setting up a sound system and/or for capturing a room impulse response
for acoustical analysis. This helps to ensure that you have sufficient
energy at all frequencies to make solid measurements. For the later stages of system
optimization with SmaartLive, using music as a test signal allows you to make qualitative
judgments as you make final adjustments to system EQs and crossover filters.
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Q: What type of computer do I
need to run SmaartLive or Smaart Acoustic Tools?
A: Recommended system requirements for both SmaartLive and Smaart Acoustic
Tools are available in the Products section of our web site.
Please note that SIA does not recommend or endorse
specific computer models for use with Smaart software products.
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Q: Do SmaartLive and Smaart
Acoustic Tools run on a laptop computer?
A: Yes. SIA SmaartLive and Smaart Acoustic Tools run on any
computer that satisfies the minimum hardware requirements (see above). Most notebook
computers have 16-bit stereo sound hardware built in and this type of sound hardware has
proven to be very acceptable for all but the most critical measurement applications. The
one caveat is that a stereo line level input is an absolute requirement.
If your computer lacks sound hardware or a line level input, there are PCMCIA sound cards
and USB audio interface devices on the market that allow you to add or upgrade notebook
audio I/O capabilities. When shopping for a new computer though, we strongly recommend
holding out for a model with a built-in line input. Even if you already plan on upgrading
the computer's audio I/O with a PCMCIA or USB device, it's nice to have access to the
internal sound hardware as a back-up.
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