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Topic: "Audiophile" listening event @ Definitive Audio in Seattle (Read 151251 times) previous topic - next topic
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"Audiophile" listening event @ Definitive Audio in Seattle

Reply #125
So, it would indeed be an interesting finding, if John Atkinson, who very likely can't hear a continuous, high volume 20 kHz tone, could suddenly hear 20 kHz, if it just faintly preceded other signals (and again not if it trailed them).


FYI, I am in my early 60s and I have my hearting tested fairly regularly. Although conventional testing only goes as high as 8kHz, my hearing sensivity below 8kHz falls within the region defined as "normal." I anecdotally test my HF cutoff on a weekly basis, as I test loudspeaker impedance by sweeping spot frequencies from 50kHz to 10Hz with the Audio Precision and noting when the tone become audible. (The output level is 6V, sourced from 600 ohms, so the spl is not high.)

I have discussed this possible paradox in Stereophile, in the context of Peter Craven's so-called "apodizing" reconstruction filter. This eliminates the conventional linear-phase "ringing" at the Nyquist frequency but introduces minimum-phase "ringing" at a slightly lower frequency.  I can indeed hear neither of these frequencies with continuous tones, so you would think that the Craven filter would have no audible effect. Similarly, none of the Keith Howard low-pass filters mentioned earlier in this thread should have an audible effect.

John Atkinson
Editor, Stereophile

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #126
I have discussed this possible paradox in Stereophile, in the context of Peter Craven's so-called "apodizing" reconstruction filter. This eliminates the conventional linear-phase "ringing" at the Nyquist frequency but introduces minimum-phase "ringing" at a slightly lower frequency.


The funny part about these magic filters like the apodizing one is that indeed the majority that looks at these impulse graphs don´t realize that all the pre and post ringing they see before the main impulse is above the cut-off frequency and out of their hearing range, even at very low amplitude with any modern correctly working resampler.

For even bigger Noobs as me seing the Apodized impulse must be a big AHA effect, impressive, time to buy!

In reality creating such an impulse graph that Apodizing marketing uses is only possible with mathematics that result in a bent phase response (that alone was an audiophile no-no back a while), a bad frequency response and what i am not sure about, it must introduce TONS of aliasing.

All this bad mathematics together may indeed change the sound
Is troll-adiposity coming from feederism?
With 24bit music you can listen to silence much louder!

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #127
I brought myself up to date and you are right, David. What I had forgotten was that the ringing frequency is a function of the cut-off frequency, so >20 kHz for the cases in discussion.

So, it would indeed be an interesting finding, if John Atkinson, who very likely can't hear a continuous, high volume 20 kHz tone, could suddenly hear 20 kHz, if it just faintly preceded other signals (and again not if it trailed them).


Just a friendly reminder that being able to hear an isolated tone at 20 KHz still doesn't confer the ability to hear bad things happening that high with real world music.

The usual sticking point for audibility up that high  is masking by program material at lower frequencies such as the 12-15 KHz range, which are usually unaffected by differences among  brick wall filters with corner frequencies in the  ca. 20 KHz range.

Understanding masking is one of those things that we who get Zwicker and Fastl et al have over your average Joe the high end audiophile or rick the recording engineer.

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #128
So, it would indeed be an interesting finding, if John Atkinson, who very likely can't hear a continuous, high volume 20 kHz tone, could suddenly hear 20 kHz, if it just faintly preceded other signals (and again not if it trailed them).


FYI, I am in my early 60s and I have my hearting tested fairly regularly. Although conventional testing only goes as high as 8kHz, my hearing sensivity below 8kHz falls within the region defined as "normal."


It is well known that it is difficult or impossible to reliably infer the performance of either people or mechanisms above 16 Khz by looking at performance below 8 KHz.

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I anecdotally test my HF cutoff on a weekly basis, as I test loudspeaker impedance by sweeping spot frequencies from 50kHz to 10Hz with the Audio Precision and noting when the tone become audible. (The output level is 6V, sourced from 600 ohms, so the spl is not high.)


I do this from time to time, and due to its casual nature, I decline to infer very much from it.

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I have discussed this possible paradox in Stereophile,


What paradox? All I see is a bunch of speculations based on completely uncontrolled evaiations that can't in any way be reaosnably called tests. No way can you reasonbly make a paradox out of conflicting speculations.

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in the context of Peter Craven's so-called "apodizing" reconstruction filter. This eliminates the conventional linear-phase "ringing" at the Nyquist frequency but introduces minimum-phase "ringing" at a slightly lower frequency.


This is false. What figures 1 and 2 of the relevant Stereophile review of the  Meridian 808i.2 show is not an elimination of linear phase ringing, but rather a reapportionment and what seems to be a significant increase in total energy in the ringing of the so-called Apodizing filter.

Looks to me like typical high end engineering - a situation that some think is ugly to look at on a scope is swapped out for artifacts that seem to be far more energetic and at a slightly lower frequency. Neither of those are exactly what I'd call positive moves. Oh yes, and you get all of that extra ringing for a far higher price.

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I can indeed hear neither of these frequencies with continuous tones, so you would think that the Craven filter would have no audible effect. Similarly, none of the Keith Howard low-pass filters mentioned earlier in this thread should have an audible effect.


As has been pointed out before JA uses what has been for decades the high end's *perfect* obfuscating smokescreen - he avoids engaging in reliable listening tests.  If you can fool enough of the paying customers some of the time and fool yourself all of the time... ;-)

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #129
So, it would indeed be an interesting finding, if John Atkinson, who very likely can't hear a continuous, high volume 20 kHz tone, could suddenly hear 20 kHz, if it just faintly preceded other signals (and again not if it trailed them).

FYI, I am in my early 60s and I have my hearting tested fairly regularly. Although conventional testing only goes as high as 8kHz, my hearing sensivity below 8kHz falls within the region defined as "normal."

It is well known that it is difficult or impossible to reliably infer the performance of either people or mechanisms above 16 Khz by looking at performance below 8 KHz.

No-one has said it does, Mr. Krueger. I mentioned it because work by Sean Olive et al has shown that it is hearing loss below 8kHz that randomizes people's judgments on audio quality.

<snip>

in the context of Peter Craven's so-called "apodizing" reconstruction filter. This eliminates the conventional linear-phase "ringing" at the Nyquist frequency but introduces minimum-phase "ringing" at a slightly lower frequency.

This is false. What figures 1 and 2 of the relevant Stereophile review of the  Meridian 808i.2 show is not an elimination of linear phase ringing, but rather a reapportionment and what seems to be a significant increase in total energy in the ringing of the so-called Apodizing filter.

The impulse response to which Mr. Krueger is referring can be found at http://www.stereophile.com/content/meridia...er-measurements . The linear phase filter "rings" at the Nyquist Frequency symmetrically before and after the single-sample impulse (fig.1). The "apodizing" filter has a null at the Nyquist frequency but "rings" only _after_ the impulse with a frequency that is of necessity lower than Nyquist (fig.2).

John Atkinson
Editor, Stereophile

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #130
For some it may be interesting in how these impulses do "ring" and how it looks spectral with Audacity.
You can see below, that all this post and pre ringing in the linear phase impulse is happening above 20kHz when done properly.
The Apodizing alike filter above is done with a non-linear sox setting.



Is troll-adiposity coming from feederism?
With 24bit music you can listen to silence much louder!

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #131
I should add for completeness an example of how sox can behave when you allow alias and choose lower bandwith. For all graphs it must be said that all these differences are in a frequency range nobody should be able to spot differences.

Is troll-adiposity coming from feederism?
With 24bit music you can listen to silence much louder!

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #132
In reality creating such an impulse graph that Apodizing marketing uses is only possible with mathematics that result in a bent phase response (that alone was an audiophile no-no back a while), a bad frequency response and what i am not sure about, it must introduce TONS of aliasing.
I don't think that's correct. The Meridian engineers report that it's linear phase up to about 18kHz. The phase response does bend above 18kHz to achieve their desired result. There's no reason there should be any aliasing at all - it can be a near-perfect low pass filter in the sense that it rejects everything above fs/2 strongly, whatever the phase response. Similarly the magnitude response in-band can be (and according to the measurements, is) flat, as it should be.

What figures 1 and 2 of the relevant Stereophile review of the  Meridian 808i.2 show is not an elimination of linear phase ringing, but rather a reapportionment and what seems to be a significant increase in total energy in the ringing of the so-called Apodizing filter.
I'm not convinced there is an increase in total energy - for one thing, the graph scales are different - for another, you're judging visually while IIRC the examples generated in a previous HA thread looked like they had different energy, when all were in fact the same (just different phase).

Cheers,
David.

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #133
The usual sticking point for audibility up that high  is masking by program material at lower frequencies such as the 12-15 KHz range, which are usually unaffected by differences among  brick wall filters with corner frequencies in the  ca. 20 KHz range.
My bet is, if anyone ever really does here a difference, it's because the ringing at 20kHz makes it may down into the audible band due to "features" in the rest of their equipment.

But as several of us keep saying, no one has proven to a useful scientific standard that this is audible. That's the first thing that should be done, not the last!

Cheers,
David.

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #134




The individual impulses are added together and the pre and post ringing is canceled out.



"Audiophile" listening event @ Definitive Audio in Seattle

Reply #135
More pictures.
I know this is known to many people here, but it could be usefull for some.





"Audiophile" listening event @ Definitive Audio in Seattle

Reply #136
The individual impulses are added together and the pre and post ringing is canceled out.
If there's signal content at/around the filter's cut-off frequency, the ringing certainly isn't cancelled out.

Cheers,
David.


"Audiophile" listening event @ Definitive Audio in Seattle

Reply #137
What figures 1 and 2 of the relevant Stereophile review of the  Meridian 808i.2 show is not an elimination of linear phase ringing, but rather a reapportionment and what seems to be a significant increase in total energy in the ringing of the so-called Apodizing filter.


I'm not convinced there is an increase in total energy - for one thing, the graph scales are different - for another, you're judging visually while IIRC the examples generated in a previous HA thread looked like they had different energy, when all were in fact the same (just different phase).


I just did a little graphics work with the web page, and find that the scale factors are identically the same, and that only the location of the origin is shifted vertically. 

The initial pulses have slightly different heights, but the taller of the two is also narrower.  I suspect that the energy content of the primary pulses are similar. 

As far as the energy in the ringing goes, the Apodized wave rings longer with several times the amplitude. 

I think we suspect that pre-ringing is somewhat more audible than post-ringing but not to the extent that several times the amplitude could be overcome.

Plus, the Apodized wave rings at an approx 10% lower frequency which is also a slight disadvantage.

I don't think that ringing this high (ca. 20 Khz)  is audible with either filter, but were things shifted down by an octave or two, Apodizing does not seem to be advantageous at all. 

That would be the interesting experiment, to move the filters' corner frequencies down until one or the other (hopefully not both!)  becomes audible, to see which one becomes audible first at the highest frequency.

If it turns out that they both become audible at the same frequency, well that's Science! ;-)

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #138
My bet is, if anyone ever really does here a difference, it's because the ringing at 20kHz makes it may down into the audible band due to "features" in the rest of their equipment.


As long as the equipment is linear, ringing at an ultrasonic corner frequency is not going to come down into the audible band.

Modern equipment now has this strong tendency to be very linear (better than 0.05 % nonlinearity), even at high frequencies.

Quote
But as several of us keep saying, no one has proven to a useful scientific standard that this is audible. That's the first thing that should be done, not the last!


I recommend testing the audibility of these efffects by shifting their frequency down utnil people start hearing them.

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #139
As long as the equipment is linear, ringing at an ultrasonic corner frequency is not going to come down into the audible band.
If the equipment is linear, and human ears don't work above 20kHz, we don't need a filter at all

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Modern equipment now has this strong tendency to be very linear (better than 0.05 % nonlinearity), even at high frequencies.
Even speakers? 0.05% = 66dB down. I'm not convinced. Though I'm doubting I could hear it even 40dB down.


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I recommend testing the audibility of these efffects by shifting their frequency down utnil people start hearing them.
I can see the logic in that - you can test anti-alias filters at lower frequencies, test dither noise at higher amplitude etc - but really, if the only way to make them audible is to change them fundamentally, then they don't matter. Whereas if they do matter - i.e. if they do cause some ABXable difference at the usual frequency or amplitude (I'm posing this is a logic problem, not fact!) then changing the frequency or amplitude to make them more audible might not be helpful at all - it might not be probing the mechanism by which they because audibly in normal use.

But it's still an interesting question: there's a point where a filter (vs no filter) becomes audible - do the differences between different filters become audible at the same frequency, or lower, or higher. It seems obvious to me that it's highly content and listener dependent - young listeners auditioning content that's rich in high frequencies and impulses should stand the best chance.

Cheers,
David.


"Audiophile" listening event @ Definitive Audio in Seattle

Reply #140
FYI, I am in my early 60s and I have my hearting tested fairly regularly. Although conventional testing only goes as high as 8kHz, my hearing sensivity below 8kHz falls within the region defined as "normal." I anecdotally test my HF cutoff on a weekly basis, as I test loudspeaker impedance by sweeping spot frequencies from 50kHz to 10Hz with the Audio Precision and noting when the tone become audible. (The output level is 6V, sourced from 600 ohms, so the spl is not high.)


Meant to add that under these conditions, my HF cutoff is around 15kHz. Didn't mean to make it look as if I was evading the question.

John Atkinson
Editor, Stereophile



"Audiophile" listening event @ Definitive Audio in Seattle

Reply #142
As long as the equipment is linear, ringing at an ultrasonic corner frequency is not going to come down into the audible band.
If the equipment is linear, and human ears don't work above 20kHz, we don't need a filter at all

Quote
Modern equipment now has this strong tendency to be very linear (better than 0.05 % nonlinearity), even at high frequencies.
Even speakers? 0.05% = 66dB down. I'm not convinced. Though I'm doubting I could hear it even 40dB down.


I was thinking about electronics. But, about those loudspeakers...

We're talking really high frequencies. Tweeters with better than 0.1 % THD at high frequencies are not rare. I've owned a number that performed that well on the test bench.

Loudspeaker nonlinearity *is* a problem at low and middle frequencies. Once you get well above the highest crossover frequency, things often settle out.

Also, the amplitude of the very high frequency content in musical program material is usually way down, like 30-40 dB below midrange. and bass.

Just about everything is pretty linear if you hit it softly enough. ;-)

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #143


I recommend testing the audibility of these efffects by shifting their frequency down utnil people start hearing them.


I can see the logic in that - you can test anti-alias filters at lower frequencies, test dither noise at higher amplitude etc - but really, if the only way to make them audible is to change them fundamentally, then they don't matter.


I agree with the idea that if going to these extremes is the only way to get positive results then they don't matter. However, I'm also a believer in basing my thinking on positive results wherever possible. So, if I know that something becomes audible only in this extreme case, then I'm a lot more comfortable saying that I know that it doesn't matter in the less extreme cases.

This also helps me predict when things become problematical.  For example I know that 20 repetitions of  D -> A -> D conversion with certain converters is not audible, but 40 repetitions are audible.  With other converters the corresponding numbers are 5 and 10. And this converter over here can be heard in just one pass.  Knowing all that I feel like I can start choosing components and configuring systems with some confidence.

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Whereas if they do matter - i.e. if they do cause some ABXable difference at the usual frequency or amplitude (I'm posing this is a logic problem, not fact!) then changing the frequency or amplitude to make them more audible might not be helpful at all - it might not be probing the mechanism by which they because audibly in normal use.


That is a philosophical possibility, but I don't know of any cases where it is an observable reality. Educate me!

Quote
But it's still an interesting question: there's a point where a filter (vs no filter) becomes audible - do the differences between different filters become audible at the same frequency, or lower, or higher. It seems obvious to me that it's highly content and listener dependent - young listeners auditioning content that's rich in high frequencies and impulses should stand the best chance.


I say line up the young listeners and tough program material and let the listening tests begin!  However, JJ tells me that there are some artifacts that are most noticable to people with certain kinds of hearing damage.

My own perosnal expereince tells me that there are people with hearing damage that are very intolerant of even just moderate listening levels. Hyperacoustisis or some such.  Mostly older people. So, listening tests are not just for the young or those with normal hearing.

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #144
That is a philosophical possibility, but I don't know of any cases where it is an observable reality.
Me Neither. At least, not with working ears and equipment. I'm sure we can find broken ears and/or equipment where it's true - i.e. there's one detection mechanism at some such amplitude or frequency, then that detection mechanism fails as you reduce amplitude or increase frequency (=inaudible) - but then some other detection mechanism kicks in further on down or up the scale (=audible again).

silly example: if you knew nothing about digital audio, and had an undithered 10-bit ADC+DAC in a box, you'd observe horribly increasing distortion as you increased the signal level (due to clipping). You'd observe the distortion reduced to very little as you decreased the signal level (below clipping). Magic - at that level the distortion is inaudible - so obviously so, and so dramatically, that who could doubt it? However, if you reduce the signal further and further, eventually you'll find that the distortion increases again (due to undithered quantisation noise).

Ultimately it's almost the same thing: a sine wave getting turned into a square wave - but happening at wildly different levels. Due to different mechanisms. And due to not doing things properly (no dither!).


Well, if there's some funny thing in human ears like that, and the ringing is audible in two different ways via two different mechanisms, then your test finds one thing, while the effect is still audible (marginally) under very different conditions. e.g. vibration of the basilar membrane detected by working inner hair cells in the region of the vibration (i.e. audible ringing - audible sound!) becomes inaudible at some such frequency BUT vibration of the basilar membrane in a region where there are no working inner hair cells, such that this motion changes the potential of outer hair cells, is marginally detectable at pretty much any frequency.

Given the complexity of the ear, and the persistent reports of something strange happening, this may be either Russell's Teapot with a huge dose of placebo, or else something that is close to reality. I'm not sure which.


IMO It's not quite on the level of homoeopathy. i.e. there's no mechanism in the world by which water can have a memory, whereas there are plenty of mechanisms by which imperfect DACs, amps, speakers and listeners can combine to make 96kHz sampling sound different from 44.1kHz sampling. So when we get positive ABX results (there have been a very few right here), we have to figure out whether it's down to things about ears that we don't understand, or due to some equipment that's not sufficiently "perfect". And so far no one has (to my satisfaction).

Cheers,
David.

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #145
I don't think that's correct. The Meridian engineers report that it's linear phase up to about 18kHz. The phase response does bend above 18kHz to achieve their desired result. There's no reason there should be any aliasing at all - it can be a near-perfect low pass filter in the sense that it rejects everything above fs/2 strongly, whatever the phase response. Similarly the magnitude response in-band can be (and according to the measurements, is) flat, as it should be.

On the Stereophile Meridian 808.2 Signature review that Peter Craven describes their Apodizing filter as new minimum-phase filter that begins rolling off below the original Nyquist frequency.
Is troll-adiposity coming from feederism?
With 24bit music you can listen to silence much louder!

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #146
I don't think that's correct. The Meridian engineers report that it's linear phase up to about 18kHz. The phase response does bend above 18kHz to achieve their desired result. There's no reason there should be any aliasing at all - it can be a near-perfect low pass filter in the sense that it rejects everything above fs/2 strongly, whatever the phase response. Similarly the magnitude response in-band can be (and according to the measurements, is) flat, as it should be.

On the Stereophile Meridian 808.2 Signature review that Peter Craven describes their Apodizing filter as new minimum-phase filter that begins rolling off below the original Nyquist frequency.


I studied up on the concept of *Apodizing* filters and found that in optics, an apodizing filter is a kind of a correcting filter. The example that was given would be a Gaussian filter that was either too light or too dark in the middle. A correcting or Apoizing filter would be added to obtain the desired response.

Catalog listing for optical apodizing filters

I conclude that an audio apodizing filter might  be a reduced-ringing low pass filter that reduces energy at high frequencies that a sharp cut-off filter whose corner frequency is at a higher frequency would turn into ringing. IOW follow a linear phase filter with a 22.05 KHz corner frequency by a minimum phase filter with a 20 KHz corner frequency to attenuate the linear phase filter's ringing at 22.05 KHz.  The apodizing filter need not provide a ton of attenuation, since the liner phase filter still reduces out-of-band responses.

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #147
Here is some interesting stuff why Benchmark Media doesn´t use Apodizing. They find its non-linearity already being a problem and they are prone to high levels of image fold back, what to my understanding is aliasing.

http://www.benchmarkmedia.com/discuss/foru...odizing-filters

On the same page they even find that there is no good evidence pre-ringing is a problem at 44.1kHz at all.

Interesting how even the business differs in seing things here.

Edit: Not the first time i have read some things at Benchmark Media or related reviews that make them look like a pretty honest manufacturer of well engineered high quality gear.
Is troll-adiposity coming from feederism?
With 24bit music you can listen to silence much louder!

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #148
Other than the text included in the title of this thread, no. All the attendees were told was that they were going to be listening to some of my hi-rez recordings.


The title of this thread is "Audiophile" listening event @ Definitive Audio in Seattle, Atkinson to demonstrate "evils of MP3"
The Stereophile blurb for the event was "John Atkinson will be demonstrating the benefits of high-resolution audio and the evils of MP3, using the master files of some of his recordings. "
So, what was the title of the presentation?

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And did you continue to use Audition 1.0's not-at-all-current mp3 codec?

No.


Which codec and settings were used for the 128kbps mp3s?


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And did you again only solicit and note responses, such as they were, after the final (128 kbps) segment?

Yes.


in that case, see previous question.


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I explained what they had been listening to. After the event, not before.



There's more than one explanation for the results you have reported.  Which one did you offer?

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As a general point, how can there be any expectation bias if the listeners are ignorant of what they will be listening to? And in this case, as all that people knew was that would be listening to a 24-bit 88.2kHz audio file, if there were any expectation bias, surely it would be in the opposite direction, ie, it would tend to make them _less_ critical of the lossy codecs?


The assumes too much.  Two issues outstanding are 1) whether the responders were (unwittingly or not) reporting a difference between the penultimate format and the final format , rather than between each format, and  2) whether there was any source of conscious or unconscious bias.  The latter are hard to rule out without rigorous methods, as you well know.

So I wonder how assertive your 'explanations' were, and how much uncertainty you acknowledged.

"Audiophile" listening event @ Definitive Audio in Seattle

Reply #149
It was only _after_ the playback that I asked them what they had noticed.


Which, itself, can be a 'loaded' question. Particularly when asked by an editor of an 'audiophile' journal that cites 'the evils of MP3', speaking at a gathering of audiophiles.

Please do try to bring this roadshow to NYC.  Short of someone posting a video, I suspect witnessing it myself is the only way I'll get substantive answers to my questions. They require more than just one-word responses.