Recently, Do not ask crime , which is frequent in Korea, is a crime that occurs on an unspecified number of people without any specific reason. The victim is concentrated in those who are classified as socially disadvantaged, such as children, women, the elderly, and the disabled, who find it difficult to resist or weaker than criminals. This, do not ask crime among crimes, such a murder crimes tend to be somewhat diminished in recent years, but the total number of crimes are steadily increasing. In particular, there are 89 cases (54%) of the 163 out of 163 crime cases, and 21 cases (13%) of public places such as subway stations, parks and elementary schools. Therefore, it is a problem that the occurrence prediction is difficult and anyone can become a victim. Various measures are being taken to prevent such crime, such as recording the distance on the CCTV, strengthening crime prevention and patrol, and setting up lighting in the dark. Personal precautions are also used to make calls using smartphones, or personal security alarms, in order to block violent crime. Using smart phones has the advantage of being able to cope with emergency situations, but it can be a disadvantage compared to portable alarms. Alarm systems, such as personal emergency alarms and whistles, there is an advantage of the alarm system shrinks the criminal mind, and to being able to get help from other people near victim. This portable security alarm is small and portable, but it is not enough to protect the victim from the assailant in terms of sound engineering. In this study, we analyze the acoustic characteristics of this portable alarm to compensate for its drawbacks.