1 in 20 children may suffer from Auditory Processing Disorder (APD).

They can hear, but have trouble understanding what they hear.

APD is a seriously under-recognised hearing problem that is an underlying cause of learning difficulties in thousands of New Zealand children. APD is not detected by standard hearing tests, but it can be diagnosed and it can be treated.

Definition of APD

Auditory Processing Disorder (APD) is a hearing disorder in which the ears process sound normally but the hearing centres and circuits of the brain don’t correctly process incoming information. This can affect understanding, especially in challenging listening situations such as in the presence of other distracting sound, or when listening to complex information or instructions.

APD is thus often referred to as a hearing problem in which “the brain can’t hear”.

APD is sometimes also referred to as CAPD or Central Auditory Processing Disorder.

Click here for an official technical definition of APD.

Prevalence of APD

The true prevalence of APD is not known.  It is estimated to affect 2-3% of children (Chermak and Musiek, 1997) though some estimates are higher. It affects more boys than girls. 

Causes of APD

Common causes of APD are:

  • hereditary factors
  • birth-related factors
  • maturational delay
  • glue ear (otitis media) in infancy or early childhood

Click here for more information on APD and otitis media.

Common signs of APD

Children with APD are usually of normal intelligence and pass standard hearing tests, but they sometimes have difficulty understanding what they hear. A child with APD will typically exhibit some of the following signs.

  • difficulty comprehending spoken language unless brief, clear and simple
  • hearing difficulty against other background sound
  • poor listening skills
  • slowness in processing spoken information
  • poor auditory memory (difficulty attending to and remembering spoken information)

Other possible signs include

  • insensitivity to tone of voice or other nuances of speech
  • sensitivity to excessive auditory stimulation (eg noisy situations)
  • extreme tiredness after school
  • problems with comprehension, language, phonics, spelling, vocabulary, reading or written language 

Amblyaudia (hearing weakness on one side)

Amblyaudia is the hearing equivalent of amblyopia or ‘lazy eye’.  Up to half of children with APD show weaker performance in one ear on certain tests.  The two ears don’t work together for optimal hearing.  Fortunately amblyaudia can be successfully treated.  SoundSkills is the only APD clinic in New Zealand providing assessment and treatment for Amblyaudia.

Click here for more on amblyaudia.*

Click here for information on amblyaudia treatment.

Effects of APD on hearing

People with APD miss parts of speech if it is too fast or too complex or if there is other competing sound present.  They may completely miss, or misunderstand, spoken information.  We need to be able to distinguish sounds of importance from all the sound around us.  We also need to know all the sounds (phonemes) that make up our language.  We need to be able to correctly distinguish between the different phonemes. Apart from not hearing correctly, children growing up with APD have difficulty correctly learning the phonemes which make up our language.  Poor phonological awareness in turn contributes to their learning difficulties.

People with APD may also have poor skills at detecting nuances of language such as changes in the meaning of statements denoted by a change in pitch or emphasis, for example to change a statement into a question, a demand or a joke.

Click here for more information on hearing skills that are affected by APD.

Secondary effects of APD

Children with undiagnosed APD may receive unfair criticism. They may also display excessive tiredness after school from the strain of listening. Their hearing difficulties, particularly in school, may lead to any of the following consequences.

  • under-achievement in school despite great effort
  • frustration
  • low self-esteem
  • difficulties with socialisation
  • withdrawal
  • anxiety
  • behaviour problems

Children with APD usually have deficiencies in their phonological awareness, which in turn leads to poor performance with comprehension, language, spelling, vocabulary, reading and written language.  Their poor hearing may also affect achievement in other areas of the curriculum.


How does it sound to have APD?

Adults with APD, particularly if it resulted from an accident so they have prior experience of good hearing, can provide insight into the experience of hearing with APD.  

Louise Carroll QSO, JP, GDPPA , MPM, Chief Executive Officer of the National Foundation for the Deaf Inc has Auditory Processing Disorder and uses hearing aids and an FM system.  She describes her hearing experience as follows.

“Without my hearing aids or FM system, speech seems fast, fragmented and confusing.  Voices lack tonality. My directional hearing is poor and voices from behind are particularly difficult to hear. It’s very difficult to distinguish a voice from any other sound that is present.  For example, if the refrigerator switches on (a sound barely noticeable to most people) it seems to me to swamp anyone speaking.

With my hearing aids I hear much better, losing only perhaps 25% of speech.  With both my hearing aids and FM system I can usually hear 100%. But I am still exhausted from listening at the end of the work day and want to take my hearing aids off as soon as I get home.”

One Auckland child with APD when first fitted with remote microphone hearing aids echoed the comment about lack of tonality in voices.  He listened to the teacher and teacher aide for a moment then remarked with surprise that they had different voices.  “I didn’t know people had different voices” he said.

Click to listen to an Audio Simulation of APD Click to listen to an Audio Simulation of APD (3423 KB)


APD and other disorders

Auditory Processing Disorder often occurs in conjunction with other disorders.  In particular there is considerable overlap with

  • Dyslexia
  • Attention Deficit Disorder/Attention Deficit Hyperactivity Disorder
  • Language Impairment
  • Reading Disorder.

94% of children in a University of Auckland study with APD also had Language Impairment and/or Reading Disorder (Sharma, Purdy, Kelly 2009).

APD can occur with any other disorder, for example Autism Spectrum Disorder.


For a detailed list of APD related terms and definitions, please read the glossary.