If you are only interested in dismantling the probe, please see the link below:

Dismantle Nor1290

The Nor1290 Sound Intensity Probe consists of several parts. Most importatantly, the probe transducers are two microphones. These are separated by a spacer. Both microphones are mounted to a preamplifier using an angular adapter.

The preamplifiers are held in place by the main probe hardware. The hardware allows for adjustment of the space between the microphones, along with angular and offset distances.

In addition, a probe rod including a probe handle with mounting option for a smartphone is considered a part of the probe.

The two microphones are of pre-polarised type, thus they do not require an external 200 V polarization voltage. The microphones are selected out of a batch of microhones to be phase-matched, ensuring the phase response is approximately the same. The phase matching plays an important role regarding the performance of the probe. The two microphones are mounted face-to-face with a spacer in-between.

The microphones are mounted on a 90-degree angular adapter. Make sure that the connection terminals are not touched or exposed to dust and contamination. The microphones are mounted by turning the microphones clockwise onto the threads when seen from the front. Please do not overtighten the microphone to the angular adaptor.

The grid on the microphone is detachable. Rotate anti-clockwise when seen from the front. Please do not overtighten the grid!

The spacer consists of two parts; one in metal and one in plastic. The plastic part of the spacer fits inside the metal part, and is exchangeable to allow for different spacings. Several distances are available, 12 mm, 25 mm and 50 mm. Note that the all spacers are a bit shorter than their names (i.e. 12 mm) indicated. This is due to the fact that the given distance is measured from diaphragm to diaphragm.

The metal part and plastic part fits into each other, and is held in place by tight fit over a gasket. Please ensure the axis through both parts are aligned when assembling the spacer parts. The acoustical properties of the metal and plastic part is the same - it does not matter which microphone has the metal part attached and vica versa.

The spacer parts are mounted onto the microphone grids, and must be removed during the calibration process. Rotate anti-clockwise to remove the spacer from the grid when the microphone is seen from the front.

More information about selecting the correct spacer may be found here:

Selecting spacer

The purpose of the preamplifiers is to condition the low-level output signal from the microphones into a noise-resistant impedance-insensitive signal. The preamplifiers are of Constant Current Power type, and thus ground, power and signal is all interconnected by two terminals.

The preamplifiers mounts onto the angular adapters via threads. Rotate the preamplifiers clockwise into the threads of the angular adapter.

To connect the preamplifiers to the probe hardware, a snap-fit connector is utilized. This allows the preamplifier to rotate freely inside the probe hardware. Carefully insert the preamplifier into the hardware and press until a "click" is heard and felt.

The probe hardware holds the microphone assembly in place, and is designed to influence the sound field minimally. Two adjustment knobs are available.

The upper adjustment knob (closest to the microphones) is for regulating the spacing distance and ensuring the micropphones are assembled together. The probe axis offset may also be adjusted here, however, centering the microphones symetrically is recommended.

The lower adjustment knob allows changing the angle of the probe relative to the probe rod. The probe hardware snaps into 45 degrees and 90 degrees positions. In-between angles may also be used by tightening the knob.

The connector side of the probe (both directly from the probe hardware and the probe rod) supplies a 7-pin Lemo connector, the standard microphone cable interface. Any standard microphone cable may be used as an interconnection between the probe or probe rod.

The probe rod has the same connector interface as a standard microphone cable. The handle slides freely over the handle by loosening the handle tightening knob, enabling all angles and positions to be selected freely.

The universal smartphone mount supports most smartphone sizes. No electrical connections are needed.

The low-frequency response of the probe is sensitive to turbulent air, and as such, the accompanying windscreen is recommended for most applications. The size of the widscreen also makes it easier to keep the distance between the probe and the device under test in many circumstances.

Sound Intensity help index