By Jeffrey Leahy
Broadside Arrays of Directional Microphones
In our earlier discussion, we learned how a broadside array of omnidirectional microphones works. However, it's worth noting that the concept extends to directional microphones as well. Much like their omnidirectional counterparts, these arrays involve strategically spacing out multiple directional microphones and then summing their signals. This technique effectively hones in on specific sounds or voices originating from the front of the array. By utilizing directional microphones instead of omnidirectional microphones as the core hardware component, a greater amount of directionality can be achieved. This leads to superior voice isolation and background noise reduction.
The interactive chart below shows a visual representation of the polar pattern formed by two spaced-apart directional microphones within a broadside configuration. Adjust the slider to modify the distance between two directional microphones in a broadside configuration. You may also select which type of microphone is used in the broadside array by selecting one of the four desired patterns above the slider. As you make changes, the chart will dynamically display visualized polar plots, illustrating the impact on directionality across various frequencies. Unlike the omnidirectional microphone that fails to provide any directionality at the low frequencies, notice that the directional microphone array always provides a base level of directionality at all frequencies, regardless of their spacing.
Two Directional Microphone Array Interactive Chart
Note, that just as with the omnidirectional microphone array, the array of directional microphones when used in a broadside configuration experience more directionality at certain frequencies than at others. The frequency range at which the array exhibits the most directionality depends on the spacing between the two microphones. To ensure a uniform directional response spanning the entire audio spectrum, the integration of additional microphones with different spacings is a viable approach. For instance, employing a total of four microphones becomes an option. One microphone pair can be positioned with large spacing to emphasize low frequencies, while a second pair can be placed close together to enhance performance at higher frequencies. This strategic implementation contributes to a balanced frequency response across the microphone array. This type of microphone array is also referred to as a nested array.