I’ve been reviewing the Gore filter documentation https://www.gore.com/system/files/2024-08/PEV-219-TEC-R2-EN-AUG24_WEB.pdf
It looks like the 333 series has about a quarter of the acoustic impedance as the 334, has slightly better insertion loss and signal to noise ratio (unless I’m misreading delta SNR), and is 4 microns thicker.
GAW333 is also a hydrophobic membrane, not oleophobic as in the 334. Unless the oleophobic membrane also repels water, the hydrophobic membrane seems more relevant to my needs (I’m constructing an enclosure that needs to withstand heavy downpours).
This makes me think GAW333 filters are a better option: better sound transmission and quality, greater durability, better water exclusion.
But interestingly, AudioMoth uses a GAW334 acoustic filter on their IPX7 waterproof case. Is there a reason to choose GAW334 over GAW333 (for my purposes) that I’m not seeing?
AudioMoth specifically uses GAW3345.09.4, which is a larger size not available in the GAW333 series. It looks like the larger size might help with insertion loss (see difference in insertion loss by filter size in figure on page 8). Are there other benefits to using a larger dimension filter that would make up for the other differences?
I’m sending this to Gore and will post their response, but I was curious if any of you had thoughts.
Here's the response I received from GORE. Very thorough.
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To answer your first question, we sell to companies, not to individuals without a valid VAT Nº, due to the fact that UK needs import duties clearance and taxes when selling from the EU.
Our MOQ for the GAW Series is 1.000 pcs..
Let me go straight to your comments.
Both GAW333/GAW334 are classified in our Shallow Immersion category and pass the IP68 test.
All your comparisons among GAW333 vs GAW334 are correct: about a quarter of the acoustic impedance, slightly better insertion loss and 4 microns “membrane” thicker. However the stack and thickness of the “whole” vent is the same.
You are right AudioMoth is using GAW334. They were evolving from previous membranes types to finally adopt the GAW334 on this size.
To answer your questions:
Is there a reason to choose GAW334 over GAW333? Both of the options are equipped with a reactive material that reproduces sound waves. GORE® Acoustics Vents vibrates. Effectively blocks contaminants from entering the housing. Both are hydrophobic, however GAW334 adds in an oleophobic treatment, in case you application may need it apart from repelling water. This makes GAW334 generally more durable. That’s the main difference among the two series. GAW333 is white and GAW334 is black.
We have more variety of dimensions for GAW334 compared to GAW333.
AudioMoth uses GAW3345.09.4. Does the larger size help with insertion loss? Are there other benefits to using a larger dimension? Kindly refer to our GORE® Acoustics Design guide 2. Assessing acoustic performance trough insertion loss.
Where it says “Insertion loss is affected by the size, material and construction of the vent, as well as the cavity design and the type of microphone, see graph below also in our GORE® Acoustics design guide.
GRAPH on the impact of the size TradeOff with Insertion loss
Please find below our GORE® Acoustics Design guide for reference.
PEV-152-R3-TEC-EN-MAY24_WEB.pdf
Hi, The case was originally used with a larger Porelle membrane that is no longer manufactured. The Gore GAW334 membrane is better than the Porelle original and is available in a similar size to the original, while the GAW333 vent is much smaller so would require new injection moulding tooling. Alex