Subject: Re: [AUDITORY] Question about level conversions From: Bob Masta <audio@xxxxxxxx> Date: Thu, 9 Mar 2023 08:02:19 -0500Not on the topic you are asking about, but I notice you are using Gaussian noise. Has anyone ever shown this to be detectable, compared to a uniform distribution? There's a nearly 8 dB penalty for using it, in reduced ability to reach high levels without distortion. See my "Comparing Noise Distributions" at <https://www.daqarta.com/dw_0agg.htm> Best regards, Bob Masta ================================= On 8 Mar 2023 at 12:38, Alejandro Osses wrote: > > Dear list, hello! > > I have a technical question about presentation levels and signal-to-noise > ratios (SNRs), as expressed in the current literature and in more classical > studies (some of the papers I have recently investigated: Richards (1992, JASA - > doi:10.1121/1.402831) and Ahumada et al (1975, JASA - doi:10.1121/1.380453)). > > I have some thoughts, which I will share next, please feel free to comment on > any of these aspects in terms of maths or concepts, or in terms of conceptual > accuracy.... > > In classical papers (think also of the work by David Green and colleagues), SNRs > are often expressed as energy with respect to N0, often reported as E/N0. In > this expression E is typically the energy of a target signal (e.g., a tone) > which is embedded in a noise, whose spectrum level is N0. I am interested to > know the mathematical expressions needed to convert between noise levels to the > appropriate target sound level. I will now give an example about how I am > currently doing such a conversion. > > The example: Let's say I have a Gaussian noise (duration=0.5 s) with > frequencies between 0 and 5 kHz, with a total RMS level of 70 dB SPL. On the > other hand, my target sounds have a centre frequency of 500 Hz, a duration of > 0.1 s, temporally centred in the noise. I want to know the level of the tone, if > E_tone/N0 needs to be 11.8 dB (this is actually from Ahumada et al (1975)). > > My calculations are as follows: > * Step 1: N0 = 33 dB/Hz (because N0 = lvl_noise - 10*log10(BW) = 70 - > 10*log10(5000) = 33 dB/Hz) > * Step 2: The energy of the tone E_tone can be calculated from the normalised > level to a duration of 1 second: E_tone = lvl_tone - 10*log10(dur_tone) = > lvl_tone + 10 dB (using dur=0.1 s) > * Step 3: At the same time: E_tone needs to have a E_tone/N0 of 11.8 dB or > E_tone > = N0 + 11.8 dB > * From Step 3 and 4: N0+11.8 = lvl_tone + 10 -----> for the current values: > lvl_tone = 33+11.8-10 = 34.8 dB > So, my tone will have a level of 34.8 dB SPL for this example. > > Am I correct with my calculation method or am I missing any important concept? > > Thank you for the feedback, > > Alejandro Osses > >