This paper shows evidence of using Sound Navigation and Ranging (SONAR) based system. SONAR system has widespread applications in underwater scenarios. We have focused on its use in real-time detection of an obstacle and guidance in accordance to the position of the nearest obstacle. The device designed and described in this paper aids the blind in obstacle avoidance. The device when embedded in a walking, stick makes the system portable, hassle-free, unobtrusive and unprecedented. There are several ETAs (Electronic Travel Aids) designed to make blind navigation independent of human assistance. The development of Sonar and Pi combination does not focus on the need of path planning instead it provides obstacle avoidance. The system requires nil preplanning making it ideal for any area and location. Some of the existing systems including GPS based system (Dhristri [1], touch and go system (hand gadget with earpiece)[2] and NAVTAR[3] focus on path planning i.e. to guide the blind from source to destination. However, the sonar-pi aid aims purely at obstacle avoidance thereby making it less bulky and increased cost-effectiveness than other systems. The designed system uses Raspberry pi 2 making it suitable for further developments.