Have you seen microphones that are used for outdoor projects? They often look different than the ones that are used indoors right? Well, that’s because these microphones require special protection due to their working environments. If you want better quality outdoor recordings, then you need to know what is a Microphone Windscreen!
I think its safe to say that for most home music producers and audio enthusiasts, the issue of getting decent quality recordings outdoors, won’t really come to mind. This is perfectly understandable, but I think if you are serious about audio engineering, it is in your best interest to understand how a windscreen will benefit your audio recordings!
Microphone Windscreen – Big Difference?
Otherwise known as windshield, a windscreen is used to reduce the unwanted effect of wind on microphones. Unlike a pop-filter, which only protects from unidirectional blasts, a windscreen filters wind coming from all directions. Some types of windscreens such as blimps and zeppelins, entirely encloses the microphone and protect its body as well.
It is very important to understand that given the extreme low frequency content of wind noise, vibrations that are induced in the housing of the microphone (due to contact from the wind) may significantly contribute to the overall noise output.
Here are the topics that we’ll be looking into:
- Shielding materials
- Design considerations
- Frequency response
- Other uses
The materials that are commonly used for windscreens are wire gauze, fabric or foam. These materials are designed to exhibit a significant acoustic impedance. The relatively low particle-velocity air pressure changes that are inherent in sound waves can pass through with minimal resistance (attenuation), but higher particle-velocity wind will be substantially disrupted.
The thickness of the material can also be increased to improve wind attenuation, but at the expense of losing high frequency audio content. This puts a limit to the practical size of most foam screens. Although foams and wire meshes may be completely self-supporting, soft fabrics and gauzes need to be stretched on frames, or laminated with coarser structural elements.
Noise attenuation increases exponentially as the spacing (distance) between the shield’s periphery and microphone capsule increases. This is due to the fact that all wind noise is generated at the first surface the air hits. For a shield that is approximately spherical in shape, the level of attenuation increases by (approximately) the cube of that distance.
Hence, larger shields will always be much more efficient in protecting against wind as compared to the smaller ones. Furthermore, full basket windshields produces an additional pressure chamber effect, which (as explained by Joerg Wuttke), for two-port (pressure gradient) microphones, allows the shield/microphone combination to act as a high-pass acoustic filter.
Since wind noise is caused by turbulence at a surface, noise reduction can be increased by reducing overall turbulence. Both aerodynamically smooth surfaces, and ones that prevent powerful vortices being generated, have been successfully used. Artificial fur is also suitable for this purpose since the fibres produce micro-turbulence and absorb energy silently.
Fur fibres (if not matted by wind and rain), are acoustically transparent. However, the woven or knitted backing can give significant acoustical attenuation. The drawback of using fur is that it is very arduous to manufacture them with consistency, and to keep in pristine condition on location. Thus, there is an interest to create new alternatives (DPA 5100, Rycote Cyclone).
The efficiency of wind noise reduction cannot be accurately specified because the effect varies greatly with frequency, and hence with the bandwidth of the microphone and audio channel. For instance, reductions are vital at very low frequencies (10–100 Hz) where strong wind energy exists, in order to avoid overloading of the audio chain. This can produce the typical “wumping” sound associated with wind.
At higher frequencies (200 Hz to 3 kHz), our ears will perceive the effect of wind as an addition to the normal noise floor, even though it has lower energy. Simple shields can attenuate the wind noise by 10 dB, and better ones can achieve up to 50 dB reduction. Regardless, the high frequency transparency should be indicated, since a high level of wind attenuation may be associated with very muffled audio.
Pop-screens and foam shields can be used (in the studio or on stage) for hygiene purposes, and to protect the sensitive parts of a microphone from grease and sweat. In some cases, they may also be used as coloured idents. Basket shields can also be designed to include a suspension system in order to isolate the microphone from shock and handling noise.
That’s about all I have for today. Do you see the need to use a windscreen for any of your microphones?
Let me know your thoughts down below, and do share this article with your friends!