The normal dls values benefit the Twinfield for about 1.5 dB compared to the HFA. There seems to be a critical age of about 40 - 50 years, beyond which a decline of dls becomes manifest.
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. This record was last updated on 07/03/2016 and may not reflect the most current and accurate biomedical/scientific data available from NLM. The corresponding record at NLM can be accessed at https://www.ncbi.nlm.nih.gov/pubmed/11805870