Look closely at a TalonFab dish and you'll see aerodynamic design features intended to manage wind noise from the outset. The first of these features is a deep focal length to diameter ratio. This allows the microphone to be recessed and out of the wind. The second feature is the rounded shape of the rim.
Edge shape
A parabolic dish in the wind is a bluff body. If the wind is at the right (or wrong!) angle then a turbulent layer of airflow can rips off the rim edge and hit the microphone. As part of designing our microphones we modeled wind noise risk using an airflow simulations as we iterated on the dish geometry. To the results in context we also simulated a reference dish representing a common moulded design - 43cm across (f/D ≈ 0.38) , capsule held at focus on a boom and a sharp trimmed rim.
Both traces use the same relative-risk scale in a moderate 6 m/s breeze. Head-on, both dishes perform well: a parabola pointed into the wind shelters its capsule in the cushion of decelerated air ahead of the bowl. The difference emerges as the wind direction changes. At its worst angle, the sharp-rimmed reference dish reaches a wind-noise risk score of 22; the 580 peaks at 15. Large dishes are generally expected to perform worse in wind. This one doesn't, thanks to the two design features mentioned above: the rim profile and the capsule position.
To isolate the effect of the edge, we ran the same 43 cm reference geometry again with one change: a 6 mm rolled lip in place of the sharp trim. The worst-direction wind-noise risk score fell from 22 to 15—similar to the larger 580 with its recessed microphone—purely because of the edge profile. A rounded lip softens the velocity spike at the rim, and gentler separation produces a weaker turbulent layer over the capsule.
Where the microphone sits
The other important design factor is where the capsule sits relative to the rim plane.
On the 580, the capsule sits just below the rim plane, inside the aperture. The flow solution puts the local air speed at the capsule at about 30% of the free-stream wind speed head-on and about 70% in a crosswind—the dish body is acting as an effective windshield. The 300 recesses its capsule 27 mm into the bowl, providing similar shelter.
The moulded-style reference uses the opposite arrangement. At the focus of a shallow dish, the capsule stands about 90 mm proud of the rim. In a crosswind, it experiences roughly 90% of the free-stream wind speed. At that point, the dish offers little protection: every gust reaches the diaphragm almost as if the dish were not there, with rim-generated turbulence on top of it.
This is a geometry choice made when the focal ratio is set. A deep dish (the 300 uses f/D ≈ 0.21) places the focus inside the bowl by design. A shallow dish puts the focus—and therefore the capsule—out in the weather, and no rim treatment can fully compensate. That is why we treat “microphone at the focus” and “microphone in clean air” as a single design problem.
The acoustics of edge rounding
The acoustic concern with rounded rims is edge diffraction: sound scattering from the rim and arriving at the capsule via a secondary path. The effect is real, but scale matters. Bird-recording wavelengths range from 43 mm at 8 kHz to more than a metre at the bottom of the band. At those wavelengths, whether the last few millimetres of the rim are square or rounded is a tiny perturbation. A few millimetres of edge radius changes the effective aperture—and therefore gain and beamwidth—by only a fraction of a percent.
Our acoustic simulation model captures the dish’s finite size well, though not fine edge diffraction itself. It shows no meaningful difference in on-axis response or beamwidth between a sharp lip and a rolled one.
So what's the "best" design?
- Depth: A recessed microphone position reduces wind noise.
- Wind: A larger roll produces a weaker shear layer and less noise. After capsule depth below the rim, lip shape is the most important geometric lever for wind performance.
- Acoustics: At audio wavelengths and practical roll diameters, the effect is near-neutral, so the roll carries essentially no acoustic penalty.
- Stiffness and durability: A rolled lip is more durable because it reduces stress concentration.
- Manufacturability: This is where 3D printing pays off. A rolled, variable-radius lip costs nothing extra in additive manufacturing; it is simply more toolpath. In moulding, a returned lip can complicate the tool and release, which helps explain why sharp, trimmed edges are so common on moulded dishes. When the rim shape is free to change, we can set it from simulation results and iterate it for each dish size instead of accepting the manufacturing constraint.
