Hi,
How does a shot gun microphone produce a narrow directional behaviour?
In what frequency is the narrow directivity valid as compared to the dimensions of the slots?
Please see the directivity plot at The Lobar/Shotgun Microphone Polar Pattern (With Mic Examples) – My New Microphone.
What phase relationship between the slots gets me a narrow focussed beam?
Please note that I am using the term beam as if its a speaker and not a mic. But I think its the same thing, in case of mic, of course there is no beam but its the ability of picking up sounds more from a particular direction.
Thanks and Regards,
WA
How does a shot gun microphone produce a narrow directional behaviour?
In what frequency is the narrow directivity valid as compared to the dimensions of the slots?
Please see the directivity plot at The Lobar/Shotgun Microphone Polar Pattern (With Mic Examples) – My New Microphone.
What phase relationship between the slots gets me a narrow focussed beam?
Please note that I am using the term beam as if its a speaker and not a mic. But I think its the same thing, in case of mic, of course there is no beam but its the ability of picking up sounds more from a particular direction.
Thanks and Regards,
WA
Last edited:
Wikipedia to rescue: Microphone - Wikipedia
ps. one of the things that make good microphone good is how it sounds off-axis, just like with loudspeakers. Few examples from my mic locker: ATM25 hypercardioid has bad sounding leakage that always bites my butt. The front might sound good but bad sounding leakage can ruin the track. On the other hand cardioid EV PL10 pretty much always sounds good enough if not very good and the leakage does not ruin the sound. ATM25 is a lot harder to get working sound out of (recording live, always some leakage) and thus it is not on every session. EV PL10 is always on something, even though it might not be the best option it has never ruined a track.
ps. one of the things that make good microphone good is how it sounds off-axis, just like with loudspeakers. Few examples from my mic locker: ATM25 hypercardioid has bad sounding leakage that always bites my butt. The front might sound good but bad sounding leakage can ruin the track. On the other hand cardioid EV PL10 pretty much always sounds good enough if not very good and the leakage does not ruin the sound. ATM25 is a lot harder to get working sound out of (recording live, always some leakage) and thus it is not on every session. EV PL10 is always on something, even though it might not be the best option it has never ruined a track.
Last edited:
Highly directional stick-shaped mics use interference to arrange that only sound from the forward axis avoids cancellations. The polar pattern will be very frequency-dependent, getting more directional at higher frequencies. Cancellations will never be very accurate alas, but you get useful gain and much rejection of unwanted noise.
Basically you just need a tube with a pattern of slots so that the forward sound all reinforces, and with care designing the slots you can get reasonable rejection off-axis for a reasonable range of frequencies - you want enough cancellation for enough directions and frequencies. Its not going to work for low frequencies where the wavelength is lots bigger than the mic.
The theory is no doubt pretty similar to waveguide couplers for microwaves.
Basically you just need a tube with a pattern of slots so that the forward sound all reinforces, and with care designing the slots you can get reasonable rejection off-axis for a reasonable range of frequencies - you want enough cancellation for enough directions and frequencies. Its not going to work for low frequencies where the wavelength is lots bigger than the mic.
The theory is no doubt pretty similar to waveguide couplers for microwaves.
SEARCH?
https://www.diyaudio.com/forums/equipment-and-tools/371258-shotgun-mic-narrow-beam.html#post6625894
Also:
(PDF) Refined acoustic modeling and analysis of shotgun microphones (don't click "Join", you get the PDF anyway)
https://www.diyaudio.com/forums/equipment-and-tools/371258-shotgun-mic-narrow-beam.html#post6625894
Also:
(PDF) Refined acoustic modeling and analysis of shotgun microphones (don't click "Join", you get the PDF anyway)