Ivie IE-35 RTA - Real Time Analysis - Manual (Page 30)

Ivie IE-33 & IE-35 Manual
page 30
Sound Pressure Level: Seat-to-Seat
The large numeral SPL reading reflects the results of the detector selected (Fast, Slow, Peak or Impulse), and
the weighting selected (A weighted, C weighted or Flat). In addition, the SPL Monitor function provides level
monitoring in octave band levels. Technically, octave band readings are level measurements and not SPL
measurements, since SPL is, by definition, a broad band measurement.
Monitoring of octave band levels is possible in the following octaves: 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz and
4 kHz. To select one of these octave centers, tap the green "Weighting" stylus button. It will toggle with succes-
sive taps from Flat to A weighted, to C weighted, to 125 Hz, 250 Hz , 500 Hz, 1 kHz, 2 kHz and 4 kHz, and back
again to Flat.
Sound Pressure Level (SPL) Seat-to-Seat
One of the highly useful functions of the IE-33 and IE-35 is the measurement of Seat-to-Seat variation. This
function can be used to measure the uniformity of sound level throughout a venue. The Seat-to-Seat function
allows you to set a reference level, which then becomes equated to 0 dB. As you move throughout the venue,
level in dB above or below the reference level is clearly indicated. As shown in the illustration across the page,
Seat-to-Seat variation is displayed in large numerals.
Additionally, there is a bar graph that displays Seat-to-Seat variation up to plus or minus 12 dB. There is also a
numeric readout which displays maximum deviation, the same data as the bar graph, except that it is not limited
to a range of plus or minus 12 dB. Of course, absolute SPL is also shown immediately above the maximum
deviation readout.
The large numeral SPL reading, as well as the bar graph and the maximum deviation readout, reflect the results
of the detector selected (Fast, Slow, Peak or Impulse), and the weighting selected (A weighted, C weighted or
Flat). In addition, just as in the SPL Monitor function, the Seat-to-Seat variation function provides level monitor-
ing in octave band levels.
Monitoring of octave band levels is possible in the following octaves, as shown in the display across the page:
125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz and 4 kHz. To select one of these octave centers, tap the green
"Weighting" stylus button. It will toggle with successive taps from Flat to A weighted, to C weighted, to 125 Hz,
to 250 Hz, to 500 Hz, to 1 kHz, to 2 kHz, to 4 kHz and back again to Flat.
Making a Seat-to-Seat Measurement
To make a Seat-to-Seat deviation measurement, tap the "Function" pop-up menu and select "Seat-to-Seat."
Next, with steady-state noise playing in the venue, select a representative spot as the reference. Once a repre-
sentative spot is located, establish it as the reference by carefully tapping the "Reset" stylus button. (This
"Reset" reference level will be remembered by the software even if Seat-to-Seat screen is left, but will not be
retained once the analyzer software program has been exited).
Hint: Tapping the "Reset" stylus button roughly
will cause microphonic noise to travel through the unit (like tapping a microphone with your finger) which will ele-
vate the noise level seen by the IE-33, or IE-35, thus setting a "false" reference level. Once the reference level
has been set, walking the venue will clearly indicate the level variation at various locations within the venue.
The type of venue will help determine the settings for the IE-33, or IE-35, when measuring Seat-to-Seat varia-
tion. The majority of venues will likely be measured in Slow response, as opposed to Fast or Peak. The band-
width and weighting applied are more likely to change from venue to venue. If the system is intended for music
reinforcement, you may want to measure Seat-to-Seat in the Flat mode to assure full-range uniformity from
Seat-to-Seat. You may also wish to measure the same venue A weighted if there are concerns about it meeting
local noise or sound level ordinances, which will likely be written around A weighted measurements.
On the other hand, venues intended primarily for voice reinforcement may likely be "rolled off" on the high end
as well as the low end. It is not unusual to encounter Seat-to-Seat measurement specifications written around
band limited noise center at 4 kHz. Both the IE-33 and the IE-35 meet this requirement nicely.