A DP-gram is a graph used in audiology to analyze the functioning of the inner ear. It specifically shows the amplitude of Distortion Product Otoacoustic Emissions (DPOAEs) as a function of f2 frequency.
Understanding DPOAEs and DP-grams
- DPOAEs: DPOAEs are sounds produced by the healthy cochlea (the inner ear's hearing organ) when it is stimulated by two tones of different frequencies (f1 and f2).
- DP-gram Creation:
- Two tones (f1 and f2) are presented to the ear.
- The frequencies (f2) are varied while keeping the sound levels constant.
- The amplitude of the generated DPOAE is measured.
- These measurements are plotted as a graph, with f2 frequencies on the x-axis and DPOAE amplitudes on the y-axis. This graph is the DP-gram.
How DP-grams are used
- Diagnostic Tool: DP-grams help audiologists assess the health of the cochlea.
- Hearing Loss: Patterns of DPOAE amplitudes across different frequencies can help identify specific types and regions of hearing loss.
- Monitoring: DP-grams can be used to monitor changes in cochlear function over time.
- Frequency Specificity: Because the graph shows DPOAEs at different f2 frequencies, it reveals how different parts of the cochlea respond to sound.
- Clinical Use: DP-grams are usually generated across a broad range of f2, f1 frequencies, at one established stimulus level in clinical settings.
Key Features of a DP-gram
| Feature | Description |
|---|---|
| X-axis | Frequency of the higher tone (f2) |
| Y-axis | Amplitude of the Distortion Product Otoacoustic Emission |
| Shape | The overall shape of the graph gives information about cochlear function |
| Peaks & Valleys | Variations in amplitude show which frequencies are producing robust emissions and where emissions are reduced, indicating possible cochlear damage. |
In summary, the DP-gram is a valuable tool in audiology for understanding the health of the cochlea by visualizing the relationship between stimulus frequency and DPOAE amplitude.
