List of common interjections used for transcriptions (they should all
start with 口 on the left side of the character):(1)

        啊      a1      'surprise, praise'
        啊      a2      'questioning'
        啊      a3      'disbelief'
        啊      a4      'answer; understanding; surprise; praise'
        哎/嗳   ai1     'dissastisfaction; reminding'
        哎呀    ai1ya1  'surprise; complaining; impatience'
        哎哟    ai1yo1  'surprise; agony'
        哎      ai2     'emphasis'(2)
        嗳/哎   ai3     'disagreement; denying'
        嗳/哎   ai4     'regret'
        唉      ai4     'disappointment'
        哈      ha1     'triumphant, satisfaction'
        哈哈    ha1ha1  'triumphant, satisfaction'
        咳      hai1    'sadness; regret; surprise'
        嘿/嗨   hei1    'drawing attention; showing pride; surprise'
        呵/嗬   he1     surprise
        哼      hng5    'dissatisfaction; disbelief'
        嗯/唔   n2/ng2  'querry'
        嗯      n3/ng3  'out of expectation'
        嗯      n4/ng4  'answer' (3)                    
        喔/噢   o1      'understanding'
        喔/噢唷 o1yo1   'surprise'
        哦      o2      'half belief half doubt'
        哦/喔   o4      'understanding'
        呸      pei1    'discarding; scolding'
        哇      wa1/wa3 'surprise'
        哟      yo1     'slight surprise'

        (1) When there's a /, choose the one on the left side. The actual
pronunciation of interjections may vary. Choose the one that closest to the
what is being pronounced AND what is being expressed.
        (2) The pronunciation of 哎 in tone 2 is not found in most standard 
dictionaries.
        (3) Use this one to transcribe the most common interjection that 
people use in a telephone conversation to indicate that they are listening.