Comment 4 for bug 1305133

This message appears to be coming from sound/usb/pcm.c: retire_playback_urb()
        /*
         * Report when delay estimate is off by more than 2ms.
         * The error should be lower than 2ms since the estimate relies
         * on two reads of a counter updated every ms.
         */
        if (abs(est_delay - subs->last_delay) * 1000 > runtime->rate * 2)
                snd_printk(KERN_DEBUG "delay: estimated %d, actual %d\n",
                        est_delay, subs->last_delay);

I think it is a totally useless message to repeat constantly and can be rate limited. Its also likely a function of your USB device firmware.