MONSTRO FAN

[Antony Newman]

In earlier Monstro sensor testing, SENSOR NOISE vs SENSOR TEMP was compared :

+) The MONSTRO sensor has minimal noise AT or HOTTER than the Target Temperature that the sensor was Calibrated at.

05 - 43 44 45 46 - 1024 pix

+) Of the ADAPTIVE FAN algorithms currently on offer - 'ADAPTIVE' is the only option that is stable (the other options often have a mind of their own and should be avoided).

+) The 'ADAPTIVE' algorithm 'wakes up' as it PASSES through a specific temperature.
If your target temperature is 44 deg C -> this means that Calibration temperature will fluctuate AROUND 44 deg C.

The problem with this:
+) 1 deg BELOW Calibration (43c) - there is NOISE
+) 1 deg ABOVE Calibration (45c) - there is NO Noise.

To MINIMISE NOISE (for my sensor)
+) Calibrate the sensor at 43,44 or (for Audio) 46 deg C - using 'Adaptive' Fan Mode
+) Change the Target Temperature to 44,45 , or (For Audio) 47 deg <- ie 1 deg C hotter.

AJ

[Antony Newman]

Even with the Monstro SENSOR CALIBRATED to 46 deg C - fan noise was AUDIBLE when the camera was NEAR the subject.

+) In ADAPTIVE mode - a rapid ramp up to 30-40% would usually 'mess up' the sound.
+) In MANUAL mode at 20% - the sensor slowly ramp up in temp introducing an unwanted time limit (before thermal runaway / unwanted image changes)

Listing to the actual type of NOISE sound coming from the camera with the Fan set at 20-30%:
+) The was a high pitched whistle / resonance (like a blade of grass under tension when blown over) - LOW LEVEL
+) There was a super high pitch frequency that was BEAMING (ie as the microphone moves, it seemed to come in an out of focus) - LOW LEVEL
+) There seems to be resonances sounds (ie stored energy) coming from the IN FRONT, TOP, RIGHT AND REVERSE sides of the camera - MID LEVEL
+) There were electrical TRANSFORMER like sounds that came up through the FAN holes on the top, and through the EXHAUST ports. - MID LEVEL
+) There is the sound of rushing air through the FANs on top - LOW LEVEL
+) There was the sound of TURBULENT air coming from the EXHAUST vents - LOW LEVEL (but louder than the TOP FAN holes).

00 - Monstro - Bare

AJ

[Antony Newman]

To investigate the root cause of the FAN NOISE, a few random attachments were created to to attach to FAN INTAKE holes - to SUCK the air away from the camera.

+) CHIMNEY PIPE - Suck un air from LEFT of the Camera. Made from light weight foam.

+) FLAT HOOD - Suck in air STRAIGHT BACK from the Camera. Made with a Heavy Duty Noise isolation material.

+) SUPER CHARGER - Suck air un a streamlined shape (PTFE piping) encased in Heavy Duty Noise isolation material

03 - Early Assortments

AJ

[Antony Newman]

Using a CALIBRATED MICROPHONE - I then tabulated a wide range of Audio DB levels at different FAN SPEEDS (20%-100%),
using a variety of combinations of the above ATTACHMENTS, and a few more items to shape the stream of air IN and OUT of the Camera.

04 - early numbers anal

AJ

[Phil Holland]

Hello Anthony,

I would investigate tonal response and DR in relationship to your findings because mostly what is going on is throwing the ISO rating out of whack and moving the black point and likely all the tones subsequently. I do believe what you think is "no noise" is actually lowering the black point.

A valid and important test to do here is to look at a grayscale ramp and compare the patches both in noise character and measured value and consistency.

To the tune of the fan noise when filming tight interiors a simple box atop with thin sound dampening panels and course air passthrough foam works a treat. I haven't had to use mine in about 2 years, but in a 6x6 room it snuffed out a bunch of sound. Pretty similar to your concept sans the tubing.

Interestingly Komodo is alarmingly quite, so there's clearly been some evolution and R&D since DSMC2 was created on this front. Which really makes Komodo and future cameras exciting for live action sound applications.

[Patrick Tresch]

Wondering where you are going but I'm really interested.
I've also done a fan hood to prevent the noise of the fans to be heard. But it has to be really small not to prevent the air from flowing and so augmenting the fan noise.

I still wonder why the engeneers decided :
- to invert the heat flow from top to bottom of the camera?
- to use 2 small fans instead of a bigger one?

I callibrated my sensor to 48c.
Unfortunately the callbiration temperature does determine the fan speed. If you want to have a different fanspeed tnan the cal map. You have to reset it manually at every startup.

Pat

[Antony Newman]

My thoughts (Speculations) at this point were:

+) MONSTRO EXAUST : The TURBULENT sound where the AIR comes out of the MONSTRO exhaust - is likely caused by a RIGHT ANGLE in the AIR PASSAGE immediately before exiting.
[Adding a CURVE to right angle bend would IMPROVE air flow / reduce noise]
+) MONSTRO EXAUST : The multiple narrow slots directing the downwards would like benefit from thicker wider slots.
[Ie same was when designing loudspeaker ports]

+) The VERY HIGH Pitched sounds : Did not Change - and eventually determined to emanate from the OLED side of the Touch Screen.
[Putting material in front of the screen stopped this sound]

+) The High Pitched fluting sounds - was transported through the Attachment (and could therefore be directed away from the Talent)
[My current theory is that this sounds is cause by the Grill placed over the two fans.

+) The Stored Energy Resonances : Interestingly, the FLAT HOOD managed to reduce this better than the SUPER CHARGER.
[Which lead me to believe the FANS inside the Camera were conducting sound into the TOP surface of the camera]

+) The TRANSFORMER sounds : These seemed to come directly from the fans, rather than a power supply elsewhere in the brain.
This sound is mostly piped through the mounted attachments (with a small amount through Exhaust - possibly due to the aforementioned right angle bouncing the sound back)

+) The 'rushing air sound' was mostly able to be suppressed, allowing a higher FAN speed before this became invasive.


.. and finally Doing this by hand takes ages by hand!

AJ

[Antony Newman]

Thanks for the insight on hush boxes and suggest colour investigations Phil.

+) In your own testing - did you reach an ideal temperature for your camera's sensor?

+) Quiet Komodo : That's great news (I'll be joining the Komodo band wagon in 2021).

AJ

Hello Anthony <snip> ..

[Antony Newman]

Hi Pat,

As always you are always ahead of me!

Here is the Hood that I created to help me understand the contribution of unwanted sound from RESONANCES through the top plate:

01 - Monstro - Hood

AJ

Wondering where you are going but I'm really interested. <snip>

Pat

[Antony Newman]

.. And so rather than spend hours trying to manually setup each fan speed, measure the response, collect, tabulated and put into Numbers, I created a Fan Noise testing harness so that everyone (myself included!) can actually put that mind at rest (or not) to compare Monstro Fan Noise.

Here is a GRAPH that compares MONSTRO with 'nothing' attached vs the 'hood' made from noise isolating material in the picture above:

RED : This is the Bare Camera
ORANGE : This is Camera with Hood.

Left of screen = Fan at 20%
Right of screen = Fan at 100%
Vertical axis = Noise in dB (this is comparative not absolute level)

05 - Bare Monstro

AJ