ETF 5.9 provides tone sweep measurements as well as MLS measurements as a free upgrade. Test signals are now stored in memory rather than on the hard drive, making test data gathering faster and the download smaller. Enhanced performance licenses can be purchased. These high performance capabilities include a phsychological model for measuring full range subjective frequency response, a new innovative type of test signal that gets reliable measurements in noisy environments and multitone IMD distortion measurements for more phsychologically realistic distortion measurements. Go to help-> About from the main menu to learn more about these new capabilities.

This solution was built for professionals in need of a high performance and fast system with no connecting wires between the computer and sound system under test. This enables users to play a test CD through the system and have only a microphone connected to the computer. Multiple microphone location measurements can be taken quickly and conveniently with only a small reduction of measurement accuracy. This solution also eliminates the need for long noise inducing cables and the need for a full duplex sound card in laptop computers. The existing full duplex mode of data taking may not work with some PC emulators. This new half duplex wireless solution may work on many of these Macintosh systems as well.

Spatial averaging uses sophisticated methods to provide the capability of power response averaging in the frequency domain. Several response measurements from different microphone locations are averaged to produce a response representing the complete room response. This form of averaging is useful for measuring the response of a system in spaces where the listener will not be placed in any particular spot in the room. Uses for this include live music venues, movie theaters, and automotive audio systems.

Context sensitive help for each measurement explains the purpose of the measurement as well as examples of good measurements. A project file is posted on this site to illustrate how ETF can be used in home applications for two channel and multichannel systems. Tutorials on the suport page explain practical, basic acoustic principles with example measurements from ETF to illustrate typical results in practice.

Many complex DSP based parameters are automatically set as required in ETF, this saves the user from having to set FFT and MLS sizes and free from tedious settings for each measurement. Multiple measurements can be displayed for easy comparison, measurements may be overlaid for further comparison.

MLS (Maximum Length sequence) is a noise signal that has rapidly gained favour in audio measurements as speed and sophistication of PC computing has increased. The measurement stimulus can be converted to an impulse response, from which all forms of frequency response, decay, and energy measurements can be obtained.

ETF uses two channel measurements (stereo) with the left measurement a straight outut-input connection on the sound card. This permits ETF to compensate for imperfect frequency response of low cost sound cards. An ETF user can adjust a software equalizer to change the tonality (spectral shape) of the noise signal without effecting a measurement result.

Although MLS it is not possible to measure in true real time with MLS, a short MLS signal (2 seconds) can be repeated with the graph updating each time a new measurement takes place. The 2 second delay is used to get the room into steady state behaviour, this kind of delay is necessary in all forms of audio measurement. This is used for placing foam absorbers and other passive acoustical devices and for adjusting equalizers.

ETF provides calibrated SPL measurements as well as a distance measurement from the signal propogation delay in travelling from the microphone to the loudspeaker. Relative phase can be determined from the impulse response measurement. These adjustments are critical in multichannel systems. Movie based multi channel sound systems often require that effect channel sounds reach the listener after the front left/right/center channels. This disadvantage of MLS is easily compensated for when using a two-channel measurement system such as ETF. ETF measures a system response through one channel and measures only the sound card response through the other channel. This allows ETF to have knowledge of the sound card response and therefore correct the measurement for sound card anomalies. This also means that sound card tone controls may be adjusted to boost low frequencies and attenuate high frequencies. This technique is known as spectral shaping. The test signal may be shaped with an equalizer or tone control to emphasise or de-emphasise any frequency region. The advantages of the other system types are therefore available in ETF through this technique.

Tests involving only low frequencies require extra output to overcome background noise in noisy situations. If low frequency background noise effects measurements, this signal may be used to generate a test signal containing only low frequencies (< 190 Hz). The low freuency option can be used where the full range signal may disturb others nearby.

Standard Measurements Provided

Impulse Response, Fractional Octave Response, Band Filtered Energy vs Time, Schroeder Integrations, 1/3 Octave Reverberation Time, Clarity & Definition. Long MLS test signals provide high precision low frequency room mode measurements. All standard measurements required to set up and optimize high fidelity sound systems are provided.

MLSSA users can now use laptops to gather information in the field for MLSSA analyzers. All measured data can be exported in ASCII format.