To dream of wailing, a prolonged crying, means you are upset. This dream of wailing was probably caused by mental & emotional states during your daytime. As dreams are known to be continuations of your themes which you experienced during your day.
In dream interpretation, the symbolism of wailing means the dreamer is trying to attract attention with this type of long sounds.
Another dream interpretation for the dream imagery of wailing is that the dreamer is trying to release pent up emotions with physical release of energy in making the wails.