I'm sorry to contradict David L., but the normal pronunciation of 'asked' in isolation or before a pause is /aest/, e.g. "This word is pronounced /aest/", "He never asked [pause]". First, the /k/ sound is elided, and second the pronunciation of '-ed' must, following the rules of phonological conditioning, be voiceless /t/, as final /s/ (and, for that matter final /k/) is voiceless.
Phonetically, however, environments vary, so the pronunciation varies. Pre-vocalically, /t/ commonly turns to /d/, e.g. "I never asked him" /aesdim/, before a consonant it's commonly elided, e.g "He never asked me" /aesmi/, "I asked first" /aesfurst/, and before voiced 'th' it's commonly assimilated towards the 'th' sound, e.g. "She asked them". These phenomena are common in the pronounciation of words in general. Hope this helps.