Ngineering N8502 Series Little Bigger Sound Modules are a great solution for adding layout-based environmental sounds to your model railroad. Each Little Bigger Sound module has a pre-recorded sound effect and includes an 8-ohm 2-1/16" 52mm speaker and a 1-1/2 watt amplifier - ideal for big sound effects such as thunderstorms. Audio output is considerably louder than on Little Sound Modules - great for use on layouts in noisy environments or on large scale layouts. Little Bigger Sound Modules work best on a clean (filtered) 12V DC power supply such as Ngineering No. 514-N3512A.