In previous work [Y. Ando and H. Hattori 1970 Journal of the Acoustical Society of America47, 1128-1130] the manner in which infants react to aircraft noise was investigated. It was found that babies born of mothers who came to a noisy area before or during the first five months of pregnancy showed little or no excitability to the noise. The subjects were 188 babies. In this report more than a thousand subjects including low-birth-weight infants were chosen to replicate previous work. Also, it was observed that the birth-rate of low-birth-weight babies increased as the noise level increased.