@article{fraim1970miniature, title = {Miniature Electret Microphones}, author = {Fraim, Freeman W. and Murphy, Preston V.}, journal = {J. Audio Eng. Soc}, volume = {18}, number = {5}, pages = {511--517}, year = {1970}, url = {https://www.aes.org/e-lib/browse.cfm?elib=1478} }