Alternatively, you can place fencing around individual plants or groups of plants. These don't need to be 8 feet tall, but they do need to tall enough to keep deer from leaning over the fence to eat. Otherwise, a top must also be placed on the fencing. Some reports indicate that fine mesh bird netting is effective when placed directly over plants.
How To Scare Away Deer
Loud sounds will frighten deer but the deer quickly adapt to their surroundings. So long term, noisemakers are not very effective. If you found a noise that was sufficiently unpleasant and could trigger if randomly, it might be effective to a limited extent, but it would be unpleasant for you and your neighbors as well.
Motion devices can be used to frighten deer but as with noisemakers, deer tend to adapt to the movements of such devices. This is also true for devices that move continually or only when triggered by the presence of deer. Once a deer decides something does not present a threat it will adapt to its presence.
You can apply treatments such as predator urine to frighten deer, but the drawback with these is that they must be frequently reapplied and are not practical for large areas. If you choose this treatment, coyote urine is the most effective, although human urine is also known to deter deer. If you are trying to protect a small flowerbed, don't mind reapplying the product as often as every week and the deer are not starved then this might be an acceptable method to protect your garden.